Lesson 1: Describing Motion and Force

Khalifa is picking up a pencil dropped on the ground. He is picking the pencil up with a force of 32N. Earth's gravity is pulling the chair down with a force of 20N. What is the net force?

The net force =

• 12N up

• 12N down

A place or object used for comparison to determine whether something is in motion

• Friction

• Reference point

• transfer enery

Which one is an example of a force pushing downward toward the ground?

• a. A bird sat on a telephone wire.

• c. A man pulled weeds in his garden.

• d. A dog tugged on a rope a child held.

The measuring unit of force is:

• a. Meter

• b. Reference point

• c. Newton

Carmen is helping load furniture and boxes onto a moving truck. She picks up boxes of her things, places them on a cart, and pushes the cart to the moving van. Which term best describes the type of force Carmen uses?

• a. contact

• b. friction

• c. gravity

• d. non contact

Mr. Wang works in a recycling center. Recyclable materials arrive at the center mixed together. Workers use magnets to separate steel cans from other items. Which two statements are true about the force between a steel can and a magnet?

• a. Gravity pushes the can toward the magnet.

• b. The force between the can and the magnet is a noncontact force.

• c. The attraction between the can and the magnet is a pull.

• d. The attraction between the can and the magnet is a push.

The force that can cause or change motion of an object by touching it

• Contact force

• Noncontact force

The force that can cause or change motion of an object without touching it

• Contact force

• Noncontact force

An example of a contact force:

• a. Gravity

• b. Friction

• c. Magnetic force

An example of a contact force:

• a. Friction

• b. Opening the door

• c. Kicking the ball

• d. All of the above