Forces

Which of the following is considered a contact force?

• the force between two magnets

• the gravitational pull of a planet

• friction between an object and air

• the force between two charged particles

Which term describes the tendency of a moving object to continue moving at the same velocity unless an unbalanced force acts on it?

• inertia

• friction

• gravity

• acceleration

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Which of the following explains why the coin falls into the glass rather than moving to the side with the index card?

• Newton’s first law of motion

• Newton’s second law of motion

• Newton’s third law of motion

• Newton’s law of universal gravitation

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Which of the following is an example of a force that acts at a distance?

• An airplane experiences friction as it moves through air.

• A book experiences a normal force as it rests on a table.

• A soccer ball experiences a force as it is kicked across a field.

• A magnet is pushed away when it is brought near the end of another magnet.

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Why is the magnetic force considered to be an action-at-a-distance force?

• Magnets must be far apart in order to exert a force.

• Magnets do not have to touch each other to experience a force.

• Magnets push each other apart to increase the distance between them.

• Magnets must be large in size in order to exert a force that is strong enough to notice.

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Why is the friction force considered to be a contact force?

• Friction affects only solid objects.

• Friction always acts in the same direction.

• Friction is produced when objects slide past one another.

• Friction acts in a direction opposite to the direction of an object’s motion.

What is the net force toward the right on the box?

• 0 N

• 50 N

• 100 N

• 2,500 N

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Jessica has two balls. One ball has a mass of 1 kg. The other ball has a mass of 2 kg. She pushes each with a force of 100 N. How does the acceleration of the two balls compare?

• The 1-kg ball accelerates the same as the 2-kg ball.

• The 1-kg ball accelerates half as much as the 2-kg ball.

• The 1-kg ball accelerates twice as much as the 2-kg ball.

• The 1-kg ball accelerates four times as much as the 2-kg ball.

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During a baseball game, a hitter strikes the ball with a bat. When this happens, the ball and the bat exert a force on each other. Why does the ball accelerate away from the bat more than the bat accelerates away from the ball?

• The ball has less mass, so it exerts less force on the bat.

• The ball has greater velocity before the collision, so the force affects the ball more than it affects the bat.

• The bat exerts more force than the ball because the batter is exerting a force on the bat as it hits the ball.

• The ball has less mass, so the equal force on the ball and the bat causes greater acceleration of the ball.

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If the sneaker remains motionless, which statement is true?

• F and F_friction have equal strength.

• F_friction has greater strength than F.

• F, F_friction, F_gravity, and F_table all have exactly the same strength.

• F_table and F_friction have the same strength, and F and F_gravity have the same strength.

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