Sci 8 Q3 W9 Review

When a hammer strikes a nail, the nail

• exerts balanced forces that helps it from moving.

• exerts a force equal to the weight of the hammer.

• exerts an unbalanced force that changes its velocity.

• exerts an equal and opposite force back on the hammer.

Angela blows air into a balloon and holds the end of it closed with her fingers. When she lets go of the end of the balloon, Angela observes that the release of the air propels the balloon. The propelling of the balloon from the release of the air is an example of which of Newton’s laws?

• For every action, there is an equal and opposite reaction.

• A force of attraction exists between any two objects with mass.

• The force of an object is the product of its mass multiplied by its acceleration.

• An object in motion tends to stay in motion unless an unbalanced force acts upon it.

Roland dropped a rubber ball straight down. After falling for 2 seconds, the ball struck the ground with a force of 50 newtons (N). Which vector illustrates the reaction force of the ground exerted on the ball?

• 25 N downward

• 50 N downward

• 100 N upward

• 50 N upward

When the two forces are applied to the moving bus, the bus will

• come to a complete stop because of unbalanced forces.

• accelerate because of unbalanced forces.

• slow down because the forces are balanced.

• move at a constant speed because the forces are balanced.

If the ball is at rest on the soccer field and the four forces shown are applied at the same time, the ball will

• move to the left.

• stay in the same position.

• resist any change in movement.

• accelerate in the direction of the smallest force.

Two forces act on a block as shown in the picture. What is the net force on the block?

• 10 N to the left

• 10 N to the right

• 30 N to the right

• 30 N to the left

The diagram shows two fans blowing air on a ball. What is the net force acting on the ball?

• 5 N to the left

• 5 N to the right

• 19 N to the right

• 19 N to the left

Which answer correctly states the energy transformation between two points?

• A. Kinetic energy is transformed to potential energy from points G to E.

• B. Kinetic energy is transformed to potential energy from points B to D.

• C. Potential energy is transformed to kinetic energy from points A to C.

• D. Potential energy is transformed to kinetic energy from points D to C.

As the ball moves from Point 3 to Point 4, which energy conversion is taking place?

• thermal to kinetic

• kinetic to thermal

• potential to kinetic

• kinetic to potential

A skateboarder runs for a few steps and then jumps on his skateboard. His initial applied energy carries him across a level surface for about 30 seconds. The skater notices that he has skated a long time without ever having to push off the ground again. What allows the skateboarder to move so long without pushing?

• Gravity does not act on the skater and board.

• The texture of the skating surface is very rough.

• Momentum increases as the length of time increases.

• There is little friction between wheels and surface.