Simple Machines — Answer Key
Part A: Fill in the Blank
Write the missing word or number on each line.
1. A skateboard ramp lets riders gain height by riding up an inclined plane.
A skateboard ramp is an inclined plane -- a flat, sloping surface that lets riders trade distance for height without jumping straight up.
2. A paint-can opener pries the lid off by working as a lever.
A paint-can opener works as a lever because you push down on one end and it pivots against the rim to pop the lid off with greater force.
3. A corkscrew twists into a cork because it is shaped like a screw.
A corkscrew has a spiral shape just like a screw, so when you twist it, the threads dig deeper into the cork with each turn.
4. A pulley is a grooved wheel with a rope that changes the direction of force.
A pulley has a grooved wheel that a rope fits into, so when you pull the rope in one direction the load moves in the opposite direction.
5. The sharp blade of a hatchet pushes wood apart because it is a wedge.
A hatchet blade is a wedge because its V-shaped edge converts the downward swing into a sideways push that forces the wood apart.
6. A pencil sharpener turns a blade around a axle to shave wood.
Inside a pencil sharpener, the blade spins around a central axle, and this wheel-and-axle action shaves thin curls of wood off the pencil.
7. Mechanical advantage describes how much a machine multiplies your force.
Mechanical advantage is a number that tells you how many times a machine multiplies the force you put in, so a higher number means the job feels easier.
8. An escalator is a moving inclined plane that carries people between floors.
An escalator is a motorized inclined plane with moving steps that carry people between different floors of a building without climbing stairs.
9. A teeter-totter balances when equal weight sits on each side of the fulcrum.
A teeter-totter is a lever that balances when equal weight sits on each side of the fulcrum, because the downward force is the same on both ends.
Part B: Matching
Match each item on the left to the correct answer on the right.
1. Match each item to its correct answer.
Axe blade
→ Wedge
Pulley
Bottle cap
→ Screw
Wheel and axle
Roller skate wheel
→ Wheel and axle
Screw
Tow-truck cable
→ Pulley
Wedge
Correct matches: Axe blade → Wedge; Bottle cap → Screw; Roller skate wheel → Wheel and axle; Tow-truck cable → Pulley.