Understanding Forces and Motion

Which statement best describes the concept of inertia?

• A force is needed to keep an object moving at constant velocity.

• The tendency of an object to resist changes to its state of motion.

• The ability of an object to accelerate when a net force acts.

• The measure of the gravitational force on an object.

If the mass of an object doubles, its inertia will:

• Double

• Halve

• Stay the same

• Increase four times

Two objects have the same net force applied. Object X has twice the mass of Object Y. How will their accelerations compare?

• Object X will accelerate twice as much as Object Y.

• Both will have the same acceleration.

• Object X will accelerate half as much as Object Y.

• Object Y will accelerate half as much as Object X.

If an object’s mass is constant and the net force acting on it doubles, its acceleration will:

• Double

• Halve

• Stay the same

• Become four times larger

A net force acts at an angle to an object’s motion. The acceleration will:

• Always be in the same direction as motion.

• Always be opposite to motion.

• Be in the same direction as the net force.

• Be perpendicular to the net force.

A book rests on a table. Which of the following is the correct action–reaction pair?

• Table pushes up on the book; book pushes down on the table.

• Gravity pulls down on the book; the table pushes up on the book.

• Book pushes down on the table; Earth pulls down on the book.

• Gravity pulls down on the book; book pushes down on the table.

A swimmer pushes backward on the water with her hands. The reaction force is:

• The water pushing the swimmer forward.

• The swimmer’s acceleration forward.

• Water resistance opposing her motion.

• Gravity pulling her downward.

Which of the following must be true for an object in translational equilibrium?

• No forces act on the object.

• The net force on the object is zero.

• The object is at rest.

• The object cannot move.

A block slides at constant speed on a rough surface. Which statement is correct?

• The applied force is greater than friction.

• The applied force equals friction.

• Friction is zero.

• The applied force is less than friction.

Which of these is not an example of a Newton’s 3rd Law pair?

• A horse pulls a cart; the cart pulls the horse.

• You push on a wall; the wall pushes on you.

• Gravity pulls on a falling rock; the rock pulls on Earth.

• A table pushes up on a book; gravity pulls down on the book.