Newton's Laws

Which of the following is the best way of stating Newton’s first law of motion?

• Objects in space move randomly and unpredictably because no forces act on them.

• Once an object at rest begins to move, it will soon begin to slow down, turn, or stop.

• Balanced forces cause an object to move, and unbalanced forces cause it to stop moving.

• Objects at rest don’t move unless an unbalanced force acts on them, and objects in motion don’t slow down, speed up, stop, or turn unless a force makes them do so.

How does inertia function in each of the illustrations below?

• Inertia causes the car and the object in orbit to accelerate.

• Inertia causes the car to stop, and it causes the object to turn back toward the Earth.

• Inertia causes the man’s body to move forward when he puts on the brake and it causes the object to keep moving in orbit around Earth.

• Inertia causes the seat belt to tighten around the man’s body, and it maintains a constant pull on the object in orbit around Earth.

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Why would an object in a spacecraft float in the air rather than fall to the floor?

• There is no gravity in space.

• None of Newton’s laws of motion applies to space.

• The force of gravity in space is less than it is on Earth.

• Inertia allows the object to overcome the force of gravity.

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According to Newton’s second law of motion, what two factors determine an object’s acceleration?

• the speed of the object and the power of inertia on the object

• the mass of the object and the amount of force applied to the object

• the shape of the object and the material from which the object is made

• the strength of gravity as it is applied to the object and the weight of the object

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According to Newton’s third law of motion, what happens whenever one object applies a force to a second object?

• The second object accelerates.

• The first object changes the mass of the second object.

• The second object applies an equal, opposite force to the first object.

• The first object and the second object begin to move, or they change the way they are moving.

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Which of the following gives the definition of inertia?

• a sudden shift in acceleration

• a continuous downward force

• the tendency of objects to resist a change in motion

• the ability of objects to move in a smooth, curving path

When you coast down a hill on a scooter, you move faster and faster. If you continue moving onto a level surface, finally you will stop moving. Which of Newton’s laws of motion explains why you stop?

• Newton’s first law explains that when you reach the bottom of the hill, you run out of energy, so you stop moving.

• Newton’s first law explains that gravity affects you when you move downhill, but not when you move on a level surface.

• Newton’s second law explains that no force acts on your scooter on the level surface, so it stops moving.

• Newton’s third law explains that friction between the tires and the ground is an unbalanced force that changes your motion.

Which question best describes the subject of Newton’s first law of motion?

• Why do objects fall naturally toward Earth?

• Is there any difference between a push and a pull?

• What happens to an object when it leaves Earth’s atmosphere?

• What makes an object start moving or change the way it is moving?

Katie sits on the ground and rests her hands on a bowling ball in front of her. She uses all her force to push the bowling ball away from her body. Next, Katie rests her hands on a soccer ball situated in front of her at the same location. She uses all her force to push the soccer ball away from her body. How does the movement of the two balls contrast?

• The soccer ball moves a greater distance because more force is acting on it.

• The soccer ball moves a greater distance because it has less mass.

• The bowling ball moves a greater distance because it has more mass.

• The bowling ball moves a shorter distance because less force is acting on it.

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A push and a pull are two examples of which of the following?

• a force

• velocity

• a law of motion

• a balanced force

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