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Simple Machines

Simple Machines

Learn how simple machines give a mechanical advantage.  Levers, pulleys, and incline planes an simple machines that can help lift or move an object.  You may not be able to lift a heavy refrigerator alone but with a simple machine you can.

Types of Simple Machines

  • Lever: A bar that turns around a fulcrum (pivot point) used to lift an object when a force is applied on the other side.
  • Incline Plane: A sloped surface used to raise an object.
  • Pulley: Used to change the direction of force and or multiply it.
Simple Machines

Simple Machine Variables

Name Variable Unit Unit Abbreviation
Work  W Joules  J
Force  F Newton N
Distance  d Meter m
Ideal Mechanical Advantage IMA None None
Actual Mechanical Advantage AMA None None

Force and Distance Tradeoff with Simple Machines

People use simple machines to:

  • Multiply force at the expense of distance
    • You can lift more weight but you need to push for a greater distance
  • Multiply distance at the expense of force.
    • You don’t need to push as far but you need to apply more force
  • Change the direction of force applied
lever simple machine

Q1: Which stickman, A or B in the animation, would have to push the lever with more force?

Stickman B is pushing less distance but will have to apply a much greater force.

Lever A and Lever B

Q2: Why would you want to use something like a lever if a simple machine?

Simple machines can help you multiply your input force (less force required to lift something) or change the direction you have to apply a force

Input and Output

  • Input (also called effort) in these equations is the work "you do" while using a simple machine. 
  • Output is the work the simple machine does because of your work.

What is the simple machines usual purpose: To lift the weight of the object a certain distance.  The output force is equal to weight of the object.

incline plane simple machine

When you use a simple machine

  • You do input work (Win= Findin)
  • The machine does output work (Wout=Foutdout)

In an ideal (perfect) situation, the work done by person and machine would be equal

Win=Wout

Findin=Foutdout

Output force will be equal to weight of the object we are trying to lift with a simple machine.

Q3: What is the weight of a 100 kg fridge?

Lifting a Fridge's Weight

FW = mg

FW = (100)(10)= 1000 N

Q4: How much work would you do to lift a 1000 N fridge 0.50 m?

W=Fd

W = (1000)(0.50)= 500 J

Q5: How much work would a lever do lifting a 1000 N fridge 0.50 m, under ideal conditions?

W = (1000)(0.50)= 500 J

Same as you

Q6: How much distance must you apply a 200 N force to lift a 1000 N fridge 0.50 m using a lever?

Q6

Mechanical Advantage (MA)

  • Mechanical Advantage represents how much a machine multiples your input force.
  • Actual Mechanical Advantage (AMA) of 2 means that you could lift a 100 N box with 50 N of input force.
  • Ideal Mechanical Advantage (IMA) of 2 means is a simple machine was 100% efficient you would be able to lift a 100 N box with 50 N of input force.

IMA: Ideal mechanical advantage

  • Assumes 100% efficiency
  • IMA is theoretical based on measurement distances
  • How long you push (din) divided by how far the object actually moves in the direction of the output force (dout)

ideal mechanical advantage

Q7: What is the ideal mechanical advantage of an incline that you apply a force of 65 N for 10 m and lift a 150 N couch 3 m?

Q7

AMA: Actual mechanical advantage

  • Assumes machine are inefficient and will lose some energy as heat
  • This equations deals with input and output forces
  • How much weight the machine lifts (Fout) divided by the force you apply (Fin)

actual mechanical advantage

Q8: What is the Actual mechanical advantage of an incline that you apply a force of 65 N for 10 m and lift a 150 N couch 3 m?

Q8

Determining a pulleys IMA

  • The IMA of a pulley system can be estimated by the number of supporting strands that suspend the object.
  • The strands that suspend the object are the ones going up from the object lifted.
Ideal Mechanical Advantage (IMA) of three pulleys

Q9: What is the ideal mechanical advantage of the pulley system in the animation?

2

Pulley with an IMA of 2
Question 9

A simple machine cannot create work or energy

  • No machine is 100% efficient or ideal
  • So in reality or "actual" some energy will be lost from the system at heat instead of output.

Use these formulas when a problem provides or asks about heat:

Win = Wout + Heat

Findin=Foutdout + Heat

Percent Efficiency Equation

  • Percent efficiency related to how efficient a machine is.  In other words, how much of the energy is lost using a machine that became heat instead of work output.
  • Percent efficiency of a machine can be determined many ways.

Percent Efficiency

Q10: What is the percent efficiency of a machine with an AMA of 2.31 and an IMA of 3.33?

Q10

Q11: A person does 1000 J of work with a machine with an AMA of 2.31 and an IMA of 3.33.  How much energy would be would turn into work output? (Use the percent efficiency solved for in Q10)

Q11

Q12: A person does 1000 J of work with a machine with an AMA of 2.31 and an IMA of 3.33.  How much energy would be would be lost as heat?

Q12

Simple Machines Problem Set

Click check answer to see the answer for any of the problems after you completed your work.  To see the work you will have to watch the end of our video for this lesson.

1. What is the output force of an incline plane used to lift a 61 kg refrigerator?

610 N

2. What “ideal” length of ramp would have to be used to raise a 610 N box to a height of 1.1 m using a force of 180 N?

3.73 m

3. Which incline would require the most input force from you to raise a 15 kg mass?  Why?

three inclines comparison

C, because it has the least input distance so the most input force

4. What is the actual mechanical advantage if Sam pushed a 610N box up an incline plane with a force of 220N?

AMA 2.77

5. What is the ideal mechanical advantage if Sam pushed a box 3.73 m up an incline plane to lift a box 1.1 m up on a truck bed?

IMA 3.39

You attempt to push a 3500 N washing machine up a 5.0 m ramp into your truck bed that stands 0.50 m above the ground.

6A. What is the ideal mechanical advantage of the ramp?

IMA 10

6B. If you need to exert a 450 N force to push the washing machine up the ramp with constant speed, what is the actual mechanical advantage?

AMA 7.78

6C. What is the efficiency of the ramp?

77.8%

7. What would the ideal mechanical advantage of this pulley system be?

Pulley System MA 4

IMA 4

8. What would the IMA of this incline plane be?

Incline Plane

IMA 3.1

9. In an ideal situation, how much force would you have to apply to lift a 50 kg box with this incline?

Incline Plane

161.29 N

Simple Machines Quiz

Simple Machines Quiz

Do you know your simple machines?

incline plane simple machine

Take our quiz to find out

1 / 14

Simple machines can't be used to multiply _________________.

You cannot create work or energy. In a perfect (ideal) scenario Win = Wout but it’s impossible for Wout to be more.  Since W=(F)(d) you create the equation (Fin)(din­)=(Fout)(dout).  This last equation shows how you can multiply force or distance

2 / 14

When energy is lost from a simple machine which of the following must be less

You cannot create work or energy. In a perfect (ideal) scenario Win = Wout but it’s impossible for Wout to be more.  In real situations Wout is less because heat is lost.

3 / 14

When energy is lost from a system it is most likely ________________.

You cannot create work or energy. In a perfect (ideal) scenario Win = Wout but it’s impossible for Wout to be more.  In real situations Wout is less because heat is lost.

4 / 14

Which is a simple machine consisting of a bar or plank that turns around a pivot point?

5 / 14

Simple Machine

The picture above is of a(n) ___________________.

6 / 14

John pushes a box up a ramp using a 10 m plank.  The box moves a vertical distance of 2 m and weighs 500 N, ideally with how much force must he push?

q1

7 / 14

A 460 N box is hoisted above a truck by John who applies 60 N of force.  What is the actual mechanical advantage of the pulley system?

q2

8 / 14

A 460 N box is hoisted above a truck by John who applies 60 N of force.  What is the actual mechanical advantage of the pulley system?

q2

9 / 14

Joe is attempting to lift a 3000 N motorcycle into a trailer 1.5 meters off the ground using a pulley system.  If Joe applies 300 N of force, what is the ideal distance he would pull on his side of the rope?

q3

10 / 14

What is the Actual Mechanical Advantage when 300 N of force is required to lift a 3000 N object?

q4

11 / 14

What length of ramp would you ideally have to use to raise an 815 N box a height of 2.10 m using a force of 165 N?

q5

12 / 14

What is the ideal mechanical advantage when a ramp of 4 meters is used to lift a 1400 N sled full of toys 1 meter off the ground pushing with a force of 500 N?

q6

13 / 14

What is the efficiency of 4 meters ramp used to lift a 1400 N sled full of toys 1 meter off the ground pushing with a force of 500 N?

q7

14 / 14

Tom pushes a 50 kg box up a 15 meter incline plane by pushing with a force of 100 N.  The end result is that the box was lifted 2 meters.  What was the efficiency of this simple machine?

q8

Your score is

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Unit 1: One Dimensional Motion
Unit 2: 2D Motion
Unit 3: Newton’s Laws and Force
Unit 4: Universal Gravitation and Circular Motion
Unit 5: Work, Power, Mechanical Advantage, and Simple Machines
Unit 6: Momentum, Impulse, and Conservation of Momentum
Unit 7: Electrostatics
Unit 8: Current and Circuits
Unit 9: Magnetism and Electromagnetism
Unit 10: Intro to Waves
Unit 11: Electromagnetic Waves
Unit 12: Nuclear Physics

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