This chapter introduces the basic concept of simple machines, which are tools that make our work easier by changing the direction or magnitude of a force. They help us move or lift heavy objects or perform tasks with less effort.
Here are the key ideas covered:
- What is a Simple Machine? A simple machine is a basic mechanical device that multiplies force or changes the direction of a force. It helps us do work with less effort, although we might have to apply the force over a longer distance.
- Effort, Load, and Fulcrum:
- Effort (E): The force we apply to the machine.
- Load (L): The force exerted by the object we want to move or overcome (often its weight).
- Mechanical Advantage (MA): This is the ratio of the load to the effort (MA = Load / Effort).
- Types of Simple Machines: The chapter likely covers the following main types:
- Inclined Plane: A sloping surface that allows us to move objects to a higher level by applying a smaller force over a longer distance. Examples: ramps, slides.
- Wedge: Two inclined planes joined back-to-back. It is used to split or separate objects or to hold things in place. Examples: axe, knife, nail.
- Pulley: A grooved wheel with a rope or cable running along the groove. Examples: flag pole pulley, crane.
- Wheel and Axle: A larger wheel attached to a smaller cylinder (axle) that rotate together. Examples: steering wheel, doorknob.
- Inclined Plane: A sloping surface that allows us to move objects to a higher level by applying a smaller force over a longer distance. Examples: ramps, slides.
Test yourself
A. Objective Questions
1. State whether the following statements are True or False.
(a) A boy does work while pushing a wall.
Answer. False
(b) A machine performs work by itself.
Answer. False
(c) In an ideal machine, work done on load is equal to the work done by effort.
Answer. True
(d) All levers are force multipliers.
Answer. False
(e) A pulley changes the direction of force.
Answer. True
(f) An inclined plane always has a mechanical advantage more than 1.
Answer. True
2. Fill in the blanks
(a) The useful work done by an actual machine is always ———than the work done on the machine.
Ans : Less
(b) In class II levers, the load is in between fulcrum and——–.
Ans : Effort
(c) The mechanical advantage of class ———- levers is always less than 1.
Ans : III
(d) A pulley is used to change——–.
Ans : The direction of effort
(e) Mechanical advantage of an inclined plane is always———-.
Ans : Greater than 1
3. Match the following
Answer.
4. Select the correct alternatives
(a) For an ideal machine, the efficiency is
- greater than unity
- less than unity
- equal to unity
- depends on the value of load
Answer : Equal to unity
(b) Mechanical advantage of a machine is defined as:
- Load X Effort
- Load / Effort
- Load + Effort
- Effort / Load
Answer : Load / Effort
(c) The mechanical advantage of a lever is equal to:
- Load arm / Effort arm
- Effort arm / Load arm
- Load arm + Effort arm
- Load arm — Effort arm
Answer : Load arm — Effort arm
(d) A pulley is used because it
- has the mechanical advantage greater than one
- has 100% efficiency
- helps to apply the force in a convenient direction
- requires more effort to raise a less load.
Answer : Helps to apply the force in a convenient direction
(e) Wheel is used with axle because
- sliding friction is less than the rolling friction
- rolling friction is less than the sliding friction
- they work as the inclined plane
- They help us to change the direction of force.
Answer : They work as the inclined plane
B. Short/Long Answer Questions
1) When is work said to be done by a force ?
Answer : Simply put, if you push something and it moves because of your push, then you’ve done work. If you push a wall and it doesn’t move, even though you’ve applied a force, no work has been done on the wall.
2) What is energy ?
Answer : Energy is just what allows things to get done. It’s the power that makes stuff move, shine, or get warm. We encounter and use it in lots of different ways every single day!
3) What do you understand by a machine ?
Answer : Machines are devices that help make tasks easier. They do this by either boosting the force we apply or changing the direction in which we apply it, which reduces the effort we need to put in.
4)What is the principle on which a machine works ?
Answer : 1 So, you might push or pull over a longer path, but with less effort than if you did the work directly.
2 It’s like trading a smaller force over a longer distance for a larger force over a shorter distance.
5) State two functions of a machine.
Answer : A machine helps to make work easier and faster.It changes the direction or magnitude of force applied.
6) Name six simple machines. Give an example of each machine.
Answer : Here are six simple machines with an example for each:
- Lever: A seesaw
- Pulley: Raising a flag on a flagpole
- Wheel and Axle: A doorknob
- Inclined Plane: A ramp
- Wedge: An axe splitting wood
- Screw: A jar lid
7) Define the term ‘work input’ and ‘work output’ in relation to a machine.
Answer :
Work Input:
It represents the amount of work we, or an external source, perform on the machine to get it to do something useful. Quantitatively, work input is determined by multiplying the magnitude of the effort force by the distance over which that force is exerted in its direction. It’s the total energy we put into the system.
Work Output:
It’s the energy that the machine successfully transfers to accomplish the intended task, such as lifting a weight or moving an object. Mathematically, work output is calculated by multiplying the magnitude of the load force by the distance over which the load is moved in its direction. This represents the beneficial work achieved by the machine.
Work Output = Load Force × Distance Load Moves (in the direction of the force)
It’s important to note that in any real-world machine, the work output will invariably be less than the work input. This discrepancy arises due to energy losses caused by factors like friction between moving parts, the generation of heat or sound, and wear and tear.
8) Explain the term mechanical advantage of a machine.
Answer :
The mechanical advantage (MA) of a machine is a measure of how much the machine multiplies the force you apply to it. In simpler terms, it tells you how much easier the machine makes your work by reducing the effort needed to move a load.
It is defined as the ratio of the load (the resistance force you are trying to overcome) to the effort (the force you apply to the machine).
Mathematically:
Mechanical Advantage (MA) = Load (L) / Effort (E)
Where:
- Load (L): The force exerted by the object you want to move or the resistance you want to overcome (e.g., the weight of an object you are lifting).
- Effort (E): The force you apply to the machine to move the load (e.g., the force you exert on the handle of a lever).
9) Define the term efficiency of a machine.
Answer :
The efficiency of a machine is a measure of how effectively it converts the energy or work input into useful energy or work output. It is the ratio of the useful work done by the machine on the load to the work done on the machine by the effort.
In simpler terms, efficiency tells us what percentage of the energy we put into a machine actually goes into doing the job we want it to do.
Mathematically, the efficiency (η) of a machine is expressed as:
Efficiency(η)=Work InputWork Output×100%
Where:
- Work Output is the useful work done by the machine in moving the load.
- Work Input is the work done by the effort applied to the machine.
10) What is an ideal machine ?
Answer :
Imagine a machine where every bit of energy you put in is completely and perfectly converted into the desired work. There’s no friction slowing things down, no heat generated as a byproduct, and no sound wasted. It’s a flawless system that follows the principles of conservation of energy with absolute precision.
Think of pushing a perfectly balanced cart on a perfectly frictionless surface. Once you give it a push, it would theoretically keep moving forever at a constant speed without you needing to apply any more force. That’s the essence of an ideal machine – maximum output with minimum input, and no energy wasted along the way.
While such a machine doesn’t exist in the real world due to the inherent presence of friction, air resistance, and other energy-dissipating factors, it serves as a crucial benchmark in physics and engineering. It allows us to understand the theoretical limits of what a machine can achieve and helps us analyze the efficiencies of real-world machines by comparing them to this ideal scenario. It’s a standard against which we measure how well our actual machines perform
11) Can a machine have an efficiency of 100% ? Give a reason to support your answer.
Answer : No, a real machine cannot have an efficiency of 100%.
Reason:
In any real machine, there are always some energy losses that occur during its operation. These losses are primarily due to:
- Friction: When moving parts of a machine rub against each other, some of the input energy is converted into heat due to friction. This heat is usually dissipated into the surroundings and is not used for doing useful work.
- Weight of Moving Parts: Some of the input energy is used to move the different parts of the machine itself, rather than solely focusing on the load.
- Other Factors: Energy can also be lost in the form of sound, vibration, or deformation of parts.
12) A machine is 75% efficient’. What do you understand by this statement ?
Answer : The statement “A machine is 75% efficient” means that only 75% of the energy or work you put into the machine is converted into useful work output. The remaining 25% of the input energy is lost or wasted, typically as heat due to friction, sound, or other factors.
13) What is a lever ?
Answer : A lever is a basic mechanical tool that works using a stiff, unbending rod that can turn around a stable, fixed point called a pivot or fulcrum. Its main job is to either make your pushing or pulling force (the effort) stronger to move something heavy (the load), or to simply change the direction in which you need to push or pull.
14) Describe three orders of levers giving an example of each. Draw neat diagrams showing the positions of fulcrum, load and effort in each kind of lever.
Answer :
Levers, simple machines that make work easier, come in three main types, or classes, based on where the pivot point (fulcrum), the resistance you’re working against (load), and the force you apply (effort) are located relative to each other.
1. First-Class Lever:
- Layout: The fulcrum is positioned between the effort and the load.
- Function: These levers can either amplify your force, change the direction of your force, or do both, depending on the distances between the fulcrum and where you apply the effort and where the load is.
Example: A seesaw. The center point where it balances is the fulcrum. One person’s weight is the load, and the other person pushing down is the effort.
Diagram:
(Your Push) Effort —– Pivot (Fulcrum) —– Load (Other Person’s Weight)
E —————— F —————— L
(Effort Arm) (Load Arm)
2. Second-Class Lever:
- Layout: The load is situated between the fulcrum and the effort.
- Function: These levers always make it easier to lift things because the effort you need to apply is always less than the weight of the load. They are designed to increase force.
Example: A wheelbarrow. The wheel is the fulcrum. The items you put in the barrow are the load. You lifting the handles upwards is the effort.
Diagram:
Pivot (Wheel) —– Load (Items) —– (Your Lift) Effort
F —————— L —————— E
(Load Arm) (Effort Arm)
3. Third-Class Lever:
- Layout: The effort is applied between the fulcrum and the load.
- Function: These levers always require you to use more force than the weight of the load. Instead of increasing force, they increase the distance or speed at which the load moves.
Example: Your forearm when you lift something. Your elbow is the fulcrum. Your bicep muscle pulling on your forearm (closer to your elbow) is the effort. The weight in your hand is the load.
Diagram:
Pivot (Elbow) —– (Muscle Pull) Effort —– Load (Weight in Hand)
F —————— E —————— L
(Effort Arm) (Load Arm)
These three categories of levers show how rearranging the positions of the fulcrum, load, and effort can change how a simple machine helps us do work, either by making us stronger or by allowing us to move things faster or further.
15) What do you mean by the mechanical advantage of a lever ?
Answer :
The mechanical advantage of a lever tells you how much easier it makes moving a load. Simply put, it’s the ratio of the force you get out (the load) compared to the force you put in (your effort).
Mathematically, we can say:
Mechanical Advantage (MA)=EffortLoad
A mechanical advantage greater than 1 means the lever multiplies your effort, making the task easier.
16) Which class of lever has the mechanical advantage always more than 1 ? Give an example.
Answer:
The second class of lever consistently exhibits a mechanical advantage greater than one.
Example:
Consider a bottle opener.
- The fulcrum is the edge of the bottle cap against which the opener is rested.
- The load is the force resisting the removal of the bottle cap, located between the fulcrum and where you apply pressure.
17) Which class of lever has the mechanical advantage always less than 1 ? Give an example.
Answer :
The second class of lever consistently exhibits a mechanical advantage greater than one.
Example:
The human forearm when lifting a weight is a prime example of a third-class lever.
- The fulcrum is the elbow joint.
18) Give one example of class I lever in each case where the mechanical advantage is
- more than 1
- equal to 1
- less than 1.
Answer :
Here are examples of a Class I lever for each case of mechanical advantage:
(a) Mechanical Advantage (MA) more than 1:
- Example:Crowbar used to lift a heavy box.
- Fulcrum: The point where the crowbar rests on a fixed object (like a block of wood) near the box.
- Load: The weight of the heavy box.
- Effort: The force you apply to the longer end of the crowbar.
- In this scenario, to gain a mechanical advantage greater than 1, you position the fulcrum closer to the load than to where you apply the effort. This makes the effort arm (the distance from the fulcrum to where you push) longer than the load arm (the distance from the fulcrum to where the crowbar contacts the box). Because the effort arm is longer, you can exert a smaller force to move a larger load.
(b) Mechanical Advantage (MA) equal to 1:
- Example:A pair of scissors (when cutting near the pivot).
- Fulcrum: The pivot point where the two blades are joined.
- Load: The resistance offered by the material being cut, acting close to the pivot.
- Effort: The force you apply to the handles.
- When you cut material very close to the pivot, the distance from the pivot to the material (load arm) is approximately equal to the distance from the pivot to where your fingers exert force on the handles (effort arm). In this specific instance, the mechanical advantage is close to 1, meaning you apply a force roughly equal to the resistance of the material. The primary benefit here is the change in the direction of the force.
(c) Mechanical Advantage (MA) less than 1:
- Example:Tweezers.
- Fulcrum: The point where the two arms of the tweezers are joined.
- Load: The object being held at the tips of the tweezers.
- Effort: The force you apply with your fingers between the fulcrum and the tips.
- In tweezers, you apply the effort closer to the fulcrum than the load. This makes the effort arm shorter than the load arm. Consequently, the mechanical advantage is less than 1. You need to apply a greater force with your fingers than the force exerted on the small object you are holding. The advantage here is the increased precision and the larger movement of the tips for a smaller movement of your fingers.
19) Name the class to which the following levers belong:
Answer:
(a) A pair of scissors — Class I lever
(b) a lemon squeezer — Class II lever
(c) a nut cracker — Class II lever
(d) a pair of sugar tongs — Class III lever
(e) a beam balance — Class I lever
(f) an oar rowing a boat — Class I lever
(g) a wheelbarrow — Class II lever
(h) a seesaw — Class I lever
(i) a pair of pliers — Class I lever
(j) a crow bar — Class I lever
20) The diagram given below shows the three kinds of levers. Name the class of each lever and give one example of each class.
Answer:
(a) Class: Third-Order Lever
In this lever, you can see that the effort is applied between the fulcrum (the pivot point on the left) and the load (the downward force on the right).
- Example: Think about using tweezers. Your fingers apply the effort in the middle, the hinge is the fulcrum, and the object you’re picking up is the load.
(b) Class: First-Order Lever
Here, the fulcrum is positioned between the effort (downward force on the left) and the load (downward force on the right).
- Example: A seesaw perfectly illustrates this. The central pivot is the fulcrum, one person pushing down is the effort, and the other person being lifted is the load.
(c) Class: Second-Order Lever
- Example: A bottle opener is a good example. The edge that hooks under the cap is the fulcrum, the cap you’re lifting is the load in the middle, and your hand pulling up on the handle provides the effort.
21) Draw diagrams to illustrate the positions of fulcrum, load and effort, in each of the following:
(a) a seesaw
(b) a beam balance
(c) a nutcracker
(d) a pair of forceps
Answer:
22) How can you increase the mechanical advantage of a lever ?
Answer : You’re spot on! To get more oomph out of a lever, think about where you’re pushing and where the thing you’re trying to move is located. If you want to make the job easier, you’ve got two main tricks: either put your effort further away from the pivot point (the fulcrum), or scoot the load you’re lifting closer to that same pivot. It’s all about the distances!
23) How does the friction at the fulcrum affect the mechanical advantage of the lever ?
Answer :
This friction acts like a sneaky resistance force. It opposes the intended motion of the lever. So, when you’re trying to lift a load, some of the effort you apply isn’t going towards moving the load itself, but rather towards overcoming this frictional drag at the fulcrum.
Because you have to expend some of your input force just to fight this friction, the effective mechanical advantage of the lever is reduced. You’ll need to apply a slightly larger effort than you would in a frictionless system to achieve the same outcome. The “ideal” mechanical advantage calculated based purely on the lengths of the effort and load arms doesn’t fully account for this energy loss due to friction.
24) State three differences between the three classes of levers.
Answer :
| Feature | First-Class Lever | Second-Class Lever | Third-Class Lever |
| Position of Fulcrum | Fulcrum is between the effort and the load. | Fulcrum is at one end, with the load in the middle. | Fulcrum is at one end, with the effort in the middle. |
| Mechanical Advantage (MA) | MA can be greater than, equal to, or less than 1, depending on the lengths of the effort and load arms. | MA is always greater than 1. It multiplies the force. | MA is always less than 1. It multiplies the distance or speed. |
| Common Applications/Examples | Seesaw, crowbar, scissors (cutting near pivot), pliers | Wheelbarrow, nutcracker, bottle opener | Tweezers, fishing rod, human forearm (lifting) |
25) What is a pulley ?
Answer : A pulley is a simple machine consisting of a wheel on an axle or shaft that is designed to support movement and change the direction of a taut cable. The wheel usually has a groove around its circumference to guide the rope or cable.
Pulleys can be used individually or in combination to lift heavy objects, transmit power, or change the direction of a force. Systems with multiple pulleys are called block and tackle and can provide significant mechanical advantage.
26) What is the mechanical advantage of an ideal pulley ?
Answer:
The mechanical advantage (MA) of an ideal single fixed pulley is equal to 1.
Reasoning:
In an ideal pulley system, we assume that the pulley and the rope are weightless and frictionless.
For a single fixed pulley:
- The pulley is attached to a stationary support.
- The rope runs over the pulley.
- To lift a load, you pull down on one side of the rope.
In this ideal scenario:
- The tension in the rope is the same throughout.
- The effort you apply downwards is equal to the tension in the rope.
- The tension in the rope upwards supports the load.
Therefore, the effort (E) required to lift the load (L) is equal to the load itself (E = L).
27) The mechanical advantage of an actual pulley is less than 1. Give a reason. What is the justification for using the pulley then ?
Answer :
How pulleys can make lifting easier by providing a mechanical advantage, the truth is that friction in the system and the weight of the pulley itself always chip away at that ideal advantage. So, you end up having to put in a little extra effort just to get things moving and to support the pulley.
Interestingly, even if a pulley setup doesn’t actually multiply your force (meaning the mechanical advantage isn’t greater than one), it’s still incredibly handy. The real magic in those situations is that a pulley can change the direction of the force you’re applying. Think about it – it’s often way more comfortable and efficient to pull down on a rope, using your body weight, rather than trying to awkwardly lift something up against gravity. That change in direction alone makes pulleys a valuable tool in countless situations!
28) Draw a neat labelled diagram showing a pulley being used to lift a load. How are load and effort related in an ideal situation?
Answer :
Consider this simple pulley arrangement: picture a wheel, the pulley itself, with a groove circling its edge. A rope runs smoothly within this groove. On one end of the rope, the object you want to lift, the load, is securely attached. On the other end, you apply your force, the effort, by pulling downwards.
To visualize this, imagine something like this:
Fixed Support
|
O (The Pulley)
/ \
/ \
/ \
/ \
/ \
/ \
Load ———- You (Applying Effort)
Now, let’s step into a perfect, theoretical world – one where there’s no friction slowing things down and the pulley itself has no weight. In this idealized situation, the connection between the load and the effort becomes wonderfully straightforward:
The Effort You Apply = The Weight of the Load
That’s the fundamental relationship in this ideal single-pulley system. The primary role of the pulley here isn’t to give you a force advantage; instead, its brilliance lies in its ability to redirect the force you apply. It transforms the upward struggle of lifting directly into a much more natural and often easier downward pull. So, you pull down, and as a result, the load gracefully moves upwards!
29) What is an inclined plane? What is its use ? Give two examples where ¡t is used.
Answer :
Instead of straining your back to hoist a heavy box straight up onto a loading dock, you can just push it up a ramp. You’re traveling a longer path, sure, but the effort needed at any given moment is significantly less. It’s a clever trade-off, like exchanging a short burst of intense energy for a sustained, gentler push or pull.
And your examples are spot on! Wheelchair ramps are such a practical application, providing essential accessibility by transforming a difficult vertical lift into a manageable slope. And who hasn’t enjoyed the gentle glide of a slide? It’s a fun way to experience the power of an inclined plane in action, letting gravity do most of the work over a longer distance.
So, in essence, the inclined plane is all about making the task of moving things vertically more manageable by spreading the required force over a greater distance. It’s a fundamental principle that pops up in all sorts of places, from ancient construction to modern-day conveniences.
30) What is a screw ? Give two examples.
Answer :
As you turn the screw, this inclined plane wedges itself between the material you’re screwing into. With each rotation, the screw moves a small distance forward, essentially using the principle of the inclined plane to convert a rotational force (your turning motion) into a linear force (the screw going into the material). This allows you to fasten things together very tightly.
Here are a couple of examples:
- Wood Screws: These are the everyday screws you use with a screwdriver to join pieces of wood. The sharp threads, which are essentially tightly wound inclined planes, bite into the wood as you turn them, creating a strong and secure hold.
- Jar Lids: Think about how a jar lid closes. It has a spiral thread that matches a similar thread on the jar. When you twist the lid, these inclined planes slide against each other, pulling the lid down tightly onto the jar and creating a seal.
So, in a nutshell, a screw is an inclined plane wrapped around a cylinder, used to fasten materials together by converting rotational motion into a strong linear force.
31) What is wheel and axle ? Give two examples.
Answer :
it’s a pretty neat little setup! Imagine two circles stuck together, one bigger than the other, both spinning around the same center. That bigger circle is the wheel, and the smaller one, often a rod going right through the wheel’s middle, is the axle.
This simple combo is a real game-changer when it comes to moving or twisting things. Think about it this way: when you push or pull on the outer edge of the wheel, your hand travels a longer distance compared to the axle in the middle. But here’s the magic – the axle, in turn, can exert a stronger force. It’s like trading a longer push for a more powerful twist or a longer turn for a faster spin. That ability to swap distance for force (or speed) is what makes the wheel and axle so handy.
You see them all over the place! Take a doorknob, for instance. The round part you grab is the wheel. When you turn it, your hand moves in a wide circle. That turning motion gets passed on to the little rod inside (the axle), which then uses that force to move the latch and unlock the door.
Another great example is a screwdriver. The handle you grip is the wheel, and the thin metal part that goes into the screw is the axle. By turning that larger handle, you create a stronger twisting force at the tip, making it much easier to drive the screw in (or take it out) than if you were just trying to turn the small shaft directly.
32) How does a wheel help in moving the axle ?
Answer :
A wheel makes moving an axle much easier by reducing friction. Instead of the axle directly rubbing against a surface as it moves, the wheel rolls. This rolling motion means that only a small part of the wheel is in contact with the surface at any given time, and the type of friction involved is significantly less than the sliding friction that would occur if the axle were dragged directly.
Think of it like this: imagine trying to slide a heavy box across the floor versus putting it on a cart with wheels. The cart (with wheels) makes it much simpler to move because the wheels roll instead of the box scraping against the floor. Similarly, a wheel allows the axle to roll smoothly along a surface, requiring much less force to move it.
33) What is a wedge ? Give two examples.
Answer :
A wedge is essentially a double-sided inclined plane that tapers to a thin edge. Instead of moving an object up the plane, you drive the wedge between objects or parts of an object to split, lift, or fasten them.
Here are two quick examples:
- An axe: The sharp, angled head of an axe is a wedge. When you swing it into wood, the wedge shape forces the wood fibers apart, splitting the log.
- A nail:As you hammer it into wood, it pushes the wood fibers aside and its shape helps to hold it firmly in place
34) Name the machine to which the following belong :
- Beam balance
- Lemon crusher
- Sugar tongs
- Ramp
- Door knob
- Needle
Answer:
Beam balance: Lever
Lemon crusher: Lever
Sugar tongs: Lever
Ramp: Inclined plane
Door knob: Wheel and axle
Needle: Wedge
35) What care would you take to increase the life span of a machine which you use ?
Answer :
Regular cleaning: Keeping it free from dust and dirt prevents wear and tear.
Proper lubrication: Oiling or greasing moving parts reduces friction.
Following instructions: Using it as intended avoids unnecessary strain.
Timely maintenance: Addressing small issues before they become big problems.
Careful operation: Avoiding rough handling and overloading.
36) Select the correct statement :
(a) A wheel barrow is a lever of class I.
(b) The efficiency of a machine is always 100%
(c) Friction in moving parts of a machine reduces its efficiency.
(d) No lever has the mechanical advantage greater than 1.
(e) It is easier to lift a load vertically up than to push it along an inclined plane.
(f) A screw is made by two inclined planes placed together.
Answer:
(c) Friction in moving parts of a machine reduces its efficiency.
1) In a machine an effort of 10 kgf is applied to lift a load of 100 kgf. What is its mechanical advantage ?
Answer:
The mechanical advantage (MA) of a machine is calculated as the ratio of the load (the force exerted by the object being moved) to the effort (the force applied to the machine):
MA = Load / Effort
In this case:
- Load = 100 kgf
- Effort = 10 kgf
Therefore, the mechanical advantage of the machine is:
MA = 100 kgf / 10 kgf = 10
The mechanical advantage of the machine is 10. This means that the machine multiplies the applied effort by a factor of 10, allowing a smaller force to lift a larger load.
2)The mechanical advantage of a machine is 5. How much load it can exert for the effort of 2 kgf ?
Answer : If a machine has a mechanical advantage of 5, it means it multiplies your effort force by five times. So, with an effort of 2 kgf, the machine can exert a load of:
Load=MechanicalAdvantage×Effort Load=5×2kgf Load=10kgf
Therefore, the machine can exert a load of 10 kgf.
3) The mechanical advantage of a machine is 2. It is used to raise a load of 15 kgf. What effort is needed ?
Answer:You want to lift a load that weighs 15 kilogram-force (kgf). Since the machine doubles your strength, you’ll need an effort that’s half the load.
So, the effort needed would be:
Effort = Load / Mechanical Advantage Effort = 15 kgf / 2 Effort = 7.5 kgf
Therefore, you would need an effort of 7.5 kgf.
4) A lever of length 100 cm has effort of 15 kgf at a distance of 40 cm from the fulcrum at one end. What load can be applied at its other end ?
Answer :
Imagine a seesaw that’s 100 cm long. The pivot point (fulcrum) is somewhere along it. On one side, 40 cm away from that pivot, there’s a force of 15 kgf pushing down (that’s the effort). We want to know how much weight (the load) we can put on the other end of the seesaw to balance it out.
Since the total length is 100 cm and the effort is 40 cm from the fulcrum, the distance from the fulcrum to the other end (where the load will be) must be 100 cm−40 cm=60 cm.
For the lever to be balanced, the turning effect (moment) on both sides of the fulcrum must be equal. The moment is calculated as force times distance from the fulcrum.
So, we have:
Effort × Effort Arm = Load × Load Arm
Plugging in the values:
15 kgf×40 cm=Load×60 cm
To find the Load, we rearrange the equation:
Load=60 cm15 kgf×40 cm
Load=60600 kgf
Load=10 kgf
So, a load of 10 kgf can be applied at the other end to balance the lever.
5) In a lever, fulcrum is at one end at a distance of 30 cm from the load and effort is at the other end at a distance of 90 cm from the load. Find :
(a) the length of load arm,
(b) the length of effort arm, and
(c) the mechanical advantage of the lever.
Answer:
(a) Length of the load arm:
The load is positioned 30 cm away from the fulcrum. Since the fulcrum is at one end, the distance between the fulcrum and the load is the length of the load arm.
Therefore, the length of the load arm is 30 cm.
(b) Length of the effort arm:
The effort is applied at the other end of the lever, and it’s 90 cm away from the load. Since the fulcrum is at the opposite end from the effort, the entire length between the fulcrum and the point where the effort is applied is the effort arm.
To find this length, we need to consider the distance from the load to the effort (90 cm) and the distance from the fulcrum to the load (30 cm). These two distances add up to the total length of the lever, which is also the length of the effort arm in this case.
So, the length of the effort arm is 30 cm+90 cm=120 cm.
(c) Mechanical advantage of the lever:
The mechanical advantage (MA) of a lever tells us how much the lever multiplies the force we apply. It’s the ratio of the effort arm’s length to the load arm’s length.
Using the values we found:
Mechanical Advantage (MA) = Length of load armLength of effort arm
MA = 30 cm120 cm
MA = 4
So, the mechanical advantage of this lever is 4. This means that the force you apply at the effort end will be multiplied by a factor of 4 to lift the load.
