Simple Machines — Answer Key
Part A: Multiple Choice
Circle the best answer for each question.
1. A bicycle uses several simple machines. Which one does the pedal and gear system act as?
A) Inclined plane
B) Wedge
C) Wheel and axle
D) Screw
The pedal and gear system on a bicycle is a wheel and axle because the pedal arm turns around a central axle, transferring your force to the chain and wheels.
2. Two pulleys used together let you lift a heavy load with even less force. What is this setup called?
A) A compound machine
B) A block and tackle
C) A double lever
D) A gear train
A block and tackle uses two or more pulleys together so the rope shares the load across multiple sections, letting you lift something heavy with much less force.
3. Which statement about work is correct?
A) Work happens only when an object moves
B) Holding a heavy book is always work
C) Simple machines create extra work
D) Work cannot involve force
In science, work only happens when a force makes an object move, so pushing against a wall does not count as work because the wall does not move.
4. A road that winds around a mountain instead of going straight up is an example of which simple machine?
A) Lever
B) Wedge
C) Pulley
D) Inclined plane
A winding mountain road is an inclined plane because it creates a long, gentle slope so cars use less force to climb than driving straight up the steep mountainside.
Part B: Fill in the Blank
Write the correct answer on each line.
1. A machine made of two or more simple machines working together is called a compound machine.
A compound machine combines two or more simple machines, like how a bicycle uses wheels and axles, levers, and pulleys all working together.
2. A pair of pliers combines two levers that pivot on a shared point.
Pliers have two lever arms connected at a shared pivot point, so squeezing the handles together multiplies your grip strength on the other end.
3. Turning a large steering wheel requires less force than turning a small knob.
A large steering wheel has a bigger radius than a small knob, so your hands travel a wider circle and you need less force to turn the axle.
4. A shovel uses a wedge to cut into soil and a lever to lift it out.
After the shovel's wedge-shaped blade cuts into the soil, you push down on the handle and the shovel pivots like a lever to lift the dirt out.
5. The trade-off with simple machines is less force but greater distance.
Simple machines always have a trade-off: you use less force to do the job, but you must move the object over a greater distance to make up for it.