Forces and Motion

The SI unit of force is the

• joule.
• meter.
• kilogram.
• newton.

When an unbalanced force acts on an object,

• the inertia of the object increases.
• the object’s motion does not change.
• the weight of the object decreases.
• the object accelerates.

When a pair of balanced forces acts on an object, the net force that results is

• greater in size than both forces combined.
• greater in size than one of the forces.
• equal in size to one of the forces.
• equal to zero.

What kind of friction occurs as a fish swims through water?

• fluid
• rolling
• sliding
• static

As you push a cereal box across a tabletop, the sliding friction acting on the cereal box

• acts in the direction of motion.
• equals the weight of the box.
• is usually greater than static friction.
• acts in the direction opposite of motion.

The forces acting on a falling leaf are

• air resistance and fluid friction.
• gravity and air resistance.
• gravity and static friction.
• weight and rolling friction.

An open parachute increases air resistance of a falling sky diver by

• decreasing the weight of the diver.
• increasing surface area.
• increasing the terminal velocity.
• reducing fluid friction.

Projectile motion is caused by

• the downward force of gravity.
• an initial forward velocity.
• a final vertical velocity.
• the downward force of gravity and an initial forward velocity.

An orange might roll off your cafeteria tray when you stop suddenly because of

• the balanced forces acting on the orange.
• the centripetal force acting on the orange.
• the friction forces acting on the orange.
• the orange’s inertia.

According to Newton’s second law of motion, the acceleration of an object equals the net force acting on the object divided by the object’s

• mass.
• momentum.
• velocity.
• weight.