Simple Machines and Efficiency Review

Simple Machines and Efficiency Review

Multiple Choice

What is effort (input) force?

• the force required by a machine in order to accomplish work (the force you put on the machine)
• the force which an effort force must overcome in order to do work on an object via a simple machine.
• the force the machine exerts on a object
• the output work times the input distance

Multiple Choice

What is resistance (output) force?

• the force required by a machine in order to accomplish work (the force you put on the machine)
• the force which an effort force must overcome in order to do work on an object via a simple machine.
• the force the machine exerts on a object
• the output work times the input distance

Multiple Choice

A simple machine is a device that helps to reduce the amount of _____ required to work.

• force
• energy
• work

Multiple Choice

____ is done when a force is applied over a distance.

• energy
• work
• force

Multiple Choice

Which of the following does a simple machine do?

• allows the users to apply less force over a longer distance
• reduce the amount of force needed to do work
• change the direction of the applied force
• all of the above

Multiple Choice

Which is an example of someone using a simple machine to do work?

• a boy runs across a football field
• a banker counts money
• a mother pushes a stroller up a ramp
• a girl eats a sandwich

Multiple Choice

The device used to raise a flag up a flag pole is an example of a 

• wheel and axle 
• lever
• inclined plane 
• pulley 

Multiple Choice

The fixed point on the lever is called 

• load
• resistance
• bar
• fulcrum

Multiple Choice

What type of simple machine is this?

• Pulley
• Screw
• Inclined Plane
• Lever

Multiple Choice

What type of simple machine is this?

• Inclined Plane
• Wheel and Axle
• Screw
• Pulley

Multiple Choice

What type of simple machine is this?

• Wheel and Axle
• Wedge
• Inclined Plane
• Screw

Multiple Choice

Something that uses a rope and can change the direction of a force.

• Wedge
• Lever
• Inclined Plane
• Pulley

Multiple Choice

What kind of simple machine is this?

• Screw
• Wheel and Axle
• Pulley
• Inclined Plane

Multiple Choice

An inclined plane wrapped around a rod forms this simple machine 

• lever
• pulley
• screw
• wedge 

Multiple Choice

What type of simple machine is this?

• Wheel and Axle
• Pulley
• Wedge
• Screw

Multiple Choice

Mechanical Advantage:  To move objects to a greater height.

• Pulley
• Wedge
• Lever
• Inclined Plane

Multiple Choice

Two examples of a pulley...

• knife & axe blade
• lightbulb & screw
• flagpole hoist & window blinds
• catapult & teeter totter

Multiple Choice

What type of simple machines does the photo show?

• Lever and wedge
• Inclined Plane and lever
• Pulley and wedge
• Lever and screw

Multiple Choice

What simple machine has a fulcrum and can be used to lift a weight?

• Pulley
• lever
• screw
• wedge

​Efficiency and Friction

• ​Mechanical Efficiency measures how well a machine converts input work into output work

• ​Ideally, we want the machine to work at 100% efficiency, but that's not always the case! Heat may be lost (or too much gained) due to friction

• ​Friction is the force that holds back the motion of sliding objects (think about trying to slide around a wooden floor with shoes on!).

• ​Friction reduces a machine's efficiency

  • ​Reducing friction can help a machine run more efficiently

    • ​We can do this by making the surface smoother or by lubricating the surface

​Efficiency

​Ways to increase the efficiency of a lever are:

1. Use a sharp-pointed fulcrum (triangle) rather than a rounded fulcrum (rock)

2. Replace the fulcrum with an oiled hinge (like on a door)

3. Use a more rigid bar

4. Use a shorter bar

Ways to increase the efficiency of a pulley are:

1. Use a grooved wheel

2. Lubricate (oil) the axle of the grooved wheel

3. Use a cable or rope that grips the grooved wheel (does not slip)

Ways to increase the efficiency of an inclined plane are:

1. Use a smoother surface on the ramp

2. Lubricate (oil) the surface of the ramp

3. Use a shorter ramp

Multiple Choice

A way to make most simple machines more efficient, what can I add?

• Water

• Oil (lubricant) 

• Heat

• Friction

Multiple Select

How can I increase the efficiency of a lever?

• Replace the fulcrum with an oiled hinge 

• Use a shorter bar

• Use a sharper fulcrum 

• Use a more rigid bar

Multiple Select

How can I increase the efficiency of a pulley?

• Use a grooved wheel

• Lubricate the axle of the grooved wheel

• Use a cable or rope that grips the grooved wheel

• You can't 

Multiple Select

How can I increase the efficiency of an inclined plane?

• Add more grip (increase the friction) on the surface of the ramp

• Use a smoother surface on the ramp

• Lubricate the surface of the ramp

• Use a shorter ramp