8th Grade Science Final Review Part 2

Gymnasts often practice on foam floors, which increase the collision time when a gymnast falls. What effect does this have on collisions?

• The force exerted by the floor on the gymnast decreases.

• The change in momentum needed to stop the gymnast is decreased.

• The force exerted by the floor on the gymnast increases.

• The change in momentum needed to stop the gymnast is increased.

An object is moving north at a constant speed. A force of 5 N begins to push the object east at the same moment that a force of 5 N begins to push it west. What will happen to the object?

• The object will continue moving north.

• The object will accelerate toward the east.

• The object will slow down and stop.

• The object will turn toward the west.

A car has a mass of 1,200 kg. What is its acceleration when the engine exerts a force of 600 N? (Formula: F=ma)

• 1,800 m/s2

• 600 m/s2

• 2 m/s2

• 0.5 m/s2

A probe is launched from Earth and lands on Mars. The gravitational acceleration on Mars is 3.7 m/s2.

Which statement best compares the mass and weight of the probe?

• The mass of the probe remains the same, but the weight of the probe increases.

• The mass of the probe remains the same, but the weight of the probe decreases.

• The mass of the probe increases, but the weight of the probe remains the same.

• The mass of the probe decreases, but the weight of the probe remains the same.

Luz, who is skydiving, is traveling at terminal velocity with her body parallel to the ground. She then changes her body position to feet first toward the ground. What happens to her motion?

• She will continue to fall at the same terminal velocity because gravity has not changed.

• She will slow down because the air resistance will increase and be greater than gravity.

• She will speed up because air resistance will decrease and be less than gravity.

• She will begin to fall in free fall because she will have no air resistance acting on her.

A person is pushing a box across a table. The measured forces on the box are 10N, 14N, -7N, -10N.

Which force is represented by -7N?

• normal force

• push force

• force of friction

• force of gravity

Which statement describes friction?

• It pulls downward on a moving object.

• It is perpendicular to the surfaces that rub together.

• It occurs in the same direction as the push force.

• It causes a change in motion.

Kiley, Jermaine, and Gunther are playing tug-of-war. Kiley and Jermaine are on the same side of the rope, and Gunther is on the other side. Kiley is exerting a force of 20 N, and Jermaine is exerting a force of 25 N.

Which force would result in a balanced force for the game?

• –45 N

• –20 N

• 20 N

• 45 N

Which is an example of negative acceleration?

• a biker who maintains a constant speed through a race

• a snowboarder who increases speed when traveling downhill

• a skateboarder who reduces speed when moving up a hill

• a runner who fluctuates speed by increasing and decreasing speed

An object is moving east, and its velocity changes from 65 m/s to 25 m/s in 10 seconds. Which describes the acceleration?

• negative acceleration of 4 m/s2

• positive acceleration of 4 m/s2

• positive acceleration of 9 m/s2

• negative acceleration of 9 m/s2