Force (free Falling unit 5)

Rena wrapped an iron nail in a piece of copper wire and connected the wire to a battery.Then she held the nail above a pile of metal shavings. What type of force caused the shavings to move toward the

nail?

• friction

• gravity

• electrical force

• magnetic force

A contact force is a force that is exerted by an object when it touches another object. Which of the following

best describes a contact force?

• An orange falling from a tree

• A magnet repelling another magnet

• A wood block sliding across the top of a desk

• Hair standing up after someone take off a wool cap

Padma is riding a bike down a hill. As she gets to the bottom, she applies the brakes to stop the bike’s forward

motion. Which of the following statements best describes an example of sliding friction acting on the bike?

• The ground pushing up on the bike

• Padma's hand squeezing the handle of the brake

• Padma's body pressing down on the seat of the bike

• The surface of the brake rubbing the rim of the front tire

Earth has a greater attraction for a human than for a hummingbird. Which of the following statements is the

most likely reason that this is true?

• The human has a greater mass than the hummingbird.

• The human has a greater length than the hummingbird.

• The human has a greater volume than the hummingbird.

• The feet of the human have a greater surface area than the feet of the hummingbird.

Gordon is making a list of forces for his science class. Which of the following should Gordon NOT list as a force?

• Mass

• Gravity

• Friction

• A push or pull

Carla pushes a toy car and lets it go. The toy car rolls and gradually comes to a stop. Which of the following statements best describes explains why the car comes to a stop?

• A force must be applied pushing the car forward in the same direction as the moving car.

• A force must be applied to the car in a direction opposite to that in which it is moving.

• A force must be applied in a direction pushing the car upward to make the car stop.

• A force must be applied in a direction pulling the car downward causing the car to stop

Gravity is a force that every object exerts on every other object. When you jump up in the air, not only does the

Earth exert a gravitational force on you, but you also exert a gravitational force on the Earth. You, of course, fall

back down to the Earth. Which of the following statements best explains why you fall back down to Earth?

• Earth exerts a gravitational force on itself.

• You don't weigh enough to affect Earth's surface.

• Your mass is very small compared to Earth's mass

• Earth's fixed orbit around the Sun keeps it from moving.

When astronauts went to the moon, they wore space suits that nearly doubled their weight. But videos show

the astronauts bouncing easily across the moon’s surface, as if their space suits weighed nothing at all. Which

statement best explains why the astronauts were able to walk so lightly on the moon’s surface?

• The moon does not exert a gravitational force.

• The moon’s gravitational force is the same as Earth’s gravitational force.

• The moon’s gravitational force is weaker than Earth’s gravitational force.

• The moon’s gravitational force is stronger than Earth’s gravitational force.

High and low tides are the regular pattern of rising and sinking ocean-water levels. They are caused when the

sun’s gravity and the moon’s gravity pull on ocean water. The moon’s gravity has a greater effect on Earth’s

oceans than the sun’s gravity. Why would the moon have a greater effect than the sun?

• The moon is not as hot as the sun.

• The moon has less mass than Earth.

• The moon has less mass than the sun.

• The moon is closer to Earth than the sun

Cara set two balls of equal mass on the table 10 cm apart. What happens to the gravitational force the balls exert on each other if she increases the distance between the balls to 100 cm?

• The gravitational force increases.

• The gravitational force decreases

• The gravitational force remains the same

• Small objects do not exert gravitational forces