Work, Power, and Simple Machines

Mechanical advantage of simple Machines

By Ms. Taylor

Simple Machines

What are they?

A device that makes work easier by changing the size or direction of a force.

Work input- work done by you on the machine.

Work output- work done by the machine on an object​.

They make work easier by increasing the work output and decreasing the work input​.

Mechanical Advantage

What is it?

• The more help from the machine the easier the task is.

• The more force made by the machine…the easier it is.

• ​A machine gives mechanical advantage (MA) when it results in greater output force than input, hence, making work easier.

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Mechanical Advantage, MA

How to interpret MA

• ​A machine that gives a MA 1 only causes a change in direction.

• ​A machine that gives a MA less than 1 usually increases the distance over which the work is done.

• ​A machine that gives a MA greater than 1 usually increases the output force (less force needed)

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Multiple Choice

The amount that input is magnified by a simple machine is known as the :

• mechanical advantage

• output force

• resistance

• none of these

Multiple Choice

A lever used to lift a heavy box has an effort arm of 4 meters and a load arm of 0.8 meters. What is the mechanical advantage of the lever?

• 1

• 5

• 2.5

• 10

Wedges

Screw

Inclined plane​

Types of Simple Machines

Lever

Wheel and axle

Pulleys​

• Straight, slanted surface

• Does not decrease amount of work needed but increases the distance.

• Same work is done but over a

greater distance.​

• longer ramp, more MA

• MA=length/height of ramp​

Inclined plane

Wedge

• A pair of incline planes that move together to pull things apart.

  ​

• MA= the longer and thinner the wedge is the more mechanical advantage it has.

Screw

• Inclined plane wrapped around a cylinder

• ​Longer the spiral and the closer the threads are together the greater mechanical advantage.

Multiple Choice

How can you decrease the effort force needed to push a weight to the top of the ramp? 

• cover the surface with carpet

• increase the length of the ramp

• increase the height of the ramp

• decrease the length of the ramp

Multiple Choice

What is the primary mechanical advantage of using the simple machine seen in the image?

• You can apply a large force and have it penetrate over a very long distance.

• You can apply a long distance and have it convert into a very short distance.

• You can apply a short distance and have it multiplied to penetrate a large distance.

• You can apply a small force to penetrate something that normally requires a large force.

Multiple Choice

A simple machine that splits an object apart is a

• inclined plane

• fulcrum

• wedge

• lever

Wheel and axle

• Two circular object of different sizes working together

  ​

• Larger the wheel the greater the MA​ (more distance). It multiplies the input force.

  ​

• MA= radius of the wheel

radius of the axle​

Classes of Lever:

• It has a bar that pivots at a fixed point.

• The fixed point is a FULCRUM.

• The applied force is the EFFORT.

• The LOAD is what is being moved.​

What are they?

Levers

Levers

Mechanical Advantage

of levers

• Generally, the closer the fulcrum is to the load, or the greater the distance between the effort and fulcrum, the less input force needed.

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Pulleys

What is it?

• Has a grooved wheel that holds a rope or cable.

• One end has the load attached.

• The other end is where the input force is applied.

• May be fixed or movable.​

• Attached to the object being moved!

• ​MA depends on the number of supporting rope segments.

• More movable pulley, reduces the force needed by that amount​.

Movable Pulleys

• DOES NOT MOVE.

• One end of rope is connected to the load and the other end is pulled.

• Makes work easier by changing force direction​

Fixed Pulleys

Pulleys

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Count number of supporting ropes then divide the weight of load by that amount to get effort (input) force needed.

​

​Mass=10N,

MA=2

Input force =10/2=5N​

​

​MA of movable Pulleys

​

Multiple Choice

This 2000 N weight is raised 1 meter by pulling 4 meters of rope. What force was required to pull the rope?

• 500 N

• 1000 N

• 2000 N

• 8000 N

Multiple Choice

If a pulley system has a mechanical advantage of 4, what does that mean?

• This means that it is 4 times easier to lift this load.

• This means you only need a quarter of the effort to lift the load.

• For example, if you lifted 100 kg, it would only take 25 kg of effort.

• All of the above

Multiple Choice

A simple machine usually used to raise a flag is a (an)

• inclined plane

• pulley

• lever

• wheel and axle

Multiple Choice

A machine with a ratio greater than 1:

• multiplies the input force so the machine would be good to help move heavy objects.

• does not multiply the force, but increases distance and speed.

• is good for lifting and moving objects quicker.

• Is not good for lifting or moving objects quicker.

Mechanical advantage

Mechanical advantage

Simple machines are used to reduce the amount of force needed to do work. This can be calculated as mechanical advantage

Multiple Choice

If we get a mechanical advantage of 1 from using a simple machine , we will have to "pay for it" with the cost of more _____________ .

• force

• distance

• mechanical advantage

• effort

Multiple Choice

Mechanical advantage is a measure of how much a machine multiplies the input

• efficiency.

• force.

• power.

• work.

Multiple Choice

A rake has an effort arm of 0.4 meters and a load arm of 1 meter. What is the mechanical advantage of the lever?

• 04

• 1

• 1.4

• 2

Multiple Choice

A lever used to lift a heavy box has an effort arm of 3 meters and a load arm of 2 meters. What is the mechanical advantage of the lever?

• 1.5

• 1

• 0.5

• 3

Multiple Choice

A lever has a load arm of 1 meters and a mechanical advantage of 6. What is the size of the effort arm.

• 2

• 4

• 6

• 8

Multiple Choice

A lever used to lift a heavy box has an effort arm of 2 meters and has a mechanical advantage of 4. What is the size of the load and a load arm ?

• 1.5

• 1

• 0.5

• 3

Multiple Choice

What is the mechanical advantage in the picture?

• 2

• 1

• 0.5

• 3

Multiple Choice

What is the mechanical advantage in the picture?

• 40

• 10

• 4

• 0.25

Multiple Choice

To increase the mechanical advantage of a lever

• make sure the fulcrum is in the middle of the lever

• move the fulcrum closer to the load

• move the fulcrum closer to the effort

• use a bigger fulcrum