Forces & Simple Machines

Forces, Gravity, Motion and Simple Machines

A review of Unit 2 - Test Prep - Fourth Grade

A push or pull that can cause motion, or cause an object to change it's motion.

​​Force

The process of moving or changing position.

​​Motion

When one force is stronger than another, the result is motion.

​​Unbalanced force

A force that resists motion (when one object rubs against another). Friction causes things to stop or slow down.

​​Friction

A force that attracts things to earth. Mass and distance determines the strength of gravity.

Gravity

is the frictional force of air. As an object moves, air resistance slows it down. The faster an object moves, the greater the resistance.

Air resistance

A long and stable body that rests on a fulcrum (support). The fulcrum is the point where the lever pivots.
wheelbarrow, shovel, see-saw, crowbar, arms and legs

Lever

Made with a looping rope over one or more wheels, used to lift heavy objects. When you pull on one rope, it creates an upward pull on the other end. Elevators are examples.

Pulley

A wheel with a rod attached in the middle as an axle to help life or move loads. Doorknobs, screwdriver, steering wheel are examples.

Wheel and axle

An inclined plane is a flat surface with one end higher than the other. It allows heavy objects to slide up to a higher point rather than be lifted. stairs, slides, ramps

Inclined plane

Screw

A special kind of inclined plane that is wrapped around a pole. This is used to lift things and hold them together. Examples are swivel jars, jar lids and screws.

Wedge

Two inclined planes back to back. It is used to push two objects apart. Examples: knives, axes, doorstops, chisels.

Multiple Choice

A student is trying to move boxes of books. All the books are the same size and weight. One box has 2 books and the other box has 10. The student claims that it will take more force to move the box with 10 books. Is the student correct?

• Yes, because all books weigh the same

• Yes, because all of the books are the same size

• Yes, because gravity is pulling less on the box with more books

• Yes, because gravity is pulling more on the box with more books.

Multiple Choice

Linda wants to do an experiment to test how weight affects motion. She will set up an experiment - putting different weights on the string to see how far the car moves. Which effect will the weights cause on the motion of the car?

• The weights added do not change the motion of the car.

• The more weights she adds, the faster the car will move, because gravity pulls the weights to the ground.

• The more weights she adds, will cause the car to move slower.

• The less weights she adds, the faster the car will move because gravity pulls the weights to the ground.

Multiple Choice

What is gravity?

• A force that slows things down

• A force that stops things from moving

• A frictional force

• A force that pulls things to the earth

Multiple Choice

What rubbing force slows things down or stops them completely?

• Friction
• Gravity
• Inertia
• Momentum

Multiple Choice

What is air resistance?

• A force that opposes the motion of objects through air
• Something that causes objects to move

• Objects being pulled to the ground

• The force that air exerts on objects at rest

Multiple Choice

What simple machine is shown here?

• Lever
• Pulley
• Inclined Plane
• Wheel and Axle

Multiple Choice

What simple machines are shown here?

• a pulley and an inclined plane

• wheel and axle

• a lever and a wedge

• screw and wedge

Multiple Choice

Which is NOT an example of a wheel and axle?

• steering wheel

• screwdriver

• wheelbarrow

• doorknob