Simple Machines — Answer Key
Part A: Fix the Sentence
Each sentence has an error. Rewrite it correctly on the line.
1. Fix the sentence:
A wheelbarrow uses an inclined plane to carry heavy loads.
Corrected: A wheelbarrow uses a lever and a wheel and axle to carry heavy loads.
A wheelbarrow combines a lever (the handles you lift) and a wheel and axle (the front wheel), not an inclined plane, to help you carry heavy loads with less effort.
2. Fix the sentence:
A jar lid opens by using a wedge.
Corrected: A jar lid opens by using a screw.
A jar lid works like a screw, not a wedge, because the grooves on the lid and jar form spiral threads that twist on and off.
3. Fix the sentence:
A fishing pole is an example of a pulley.
Corrected: A fishing pole is an example of a lever.
A fishing pole is a lever, not a pulley, because you push down on one end of the pole and it pivots to lift the fish on the other end.
Part B: Fill in the Blank
Write the missing word or number on each line.
1. A pulley is used on a flagpole to raise and lower the flag with a rope.
A pulley is the grooved wheel at the top of the flagpole that lets you pull the rope down to raise the flag up, changing the direction of your force.
2. When you use a simple machine, you trade less force for more distance.
Simple machines let you use less force, but you must move the object over a greater distance to do the same amount of work.
3. A shovel works as a wedge when you push it into the ground to dig.
The sharp, thin blade of a shovel acts as a wedge because it pushes dirt apart as you press it into the ground.
4. A skateboard ramp is an inclined plane that helps riders gain height.
A skateboard ramp is an inclined plane because it is a flat, sloped surface that lets riders ride upward to gain height.
Part C: True or False?
Read each statement. Circle True or False.
1. A faucet handle is a type of wheel and axle.
True False
True. When you turn a faucet handle, the handle acts as the wheel and the valve stem inside acts as the axle, making it easier to open the water flow.
2. Simple machines create extra energy to do work.
True False
False. Simple machines do not create extra energy; they only change the direction or amount of force you need, so the total work stays the same.
3. A screw has threads that act like a tiny inclined plane.
True False
True. The threads on a screw are really a tiny inclined plane wrapped in a spiral, which is why turning a screw pulls it into the material a little at a time.