Force and Motion

Rebecca is practicing her aim by throwing a ball at a target.

The ball exerts a force on the target, causing the target to fall over. But when this happens, the ball bounces backward. Why does the ball bounce backward?

• The ball exerts a larger force on the target, causing the target to have a larger change of motion than the ball.

• The target exerts the same size force on the ball, so when the target moves in one direction, the ball moves in the opposite direction.

• The ball exerts a smaller force on the target because the ball is smaller than the target, so the target causes the ball to bounce backward.

• The target exerts a larger force on the ball because the ball is very bouncy.

Tags

NGSS.MS-PS2-1

A box has two forces acting on it. One force is 100 N upward. Another force is 50 N downward. What is the net force on the box?

• 100 N upward

• 50 N upward

• 50 N downward

• 100 N downward

Tags

NGSS.MS-PS2-2

Why is 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.

Michael watched the path a baseball followed after a pitcher threw it. He noticed that the ball traveled horizontally away from the pitcher as well as downward toward the ground. What force caused the ball to accelerate in the downward direction when it was thrown?

• electrical force

• air resistance

• gravitational force

• applied force

Tags

NGSS.MS-PS2-2

NGSS.MS-PS2-4

A bird flies at 12.5 meters/second. The wind speed is 4.5 m/s.

What is the speed of the bird when it flies with the wind?

• 12.5 m/s

• 4.5 m/s

• 17 m/s

• 8 m/s

Tags

NGSS.MS-PS2-2

NGSS.MS-PS3-1

A bird flies at 12.5 meters per second. The wind speed is 4.5 meters per second.

What is the speed of the bird when it against the wind?

• 17 m/s

• 8 m/s

• 12.5 m/s

• 4.5 m/s

In which situation is it better to have low friction?

• a student walks down a hallway

• a hockey puck slides toward the goal

• a ladder leans against the wall

• a skydiver uses a parachute

Two basketballs are sitting 1 m apart and are not moving. Which best explains why the gravitational force does not cause them to move?

• No gravitational force exists between the two objects because they are not touching.

• No gravitational force exists between the two objects because their masses are small.

• The gravitational force between the two objects is weak because they are 1 m apart.

• The gravitational force between the two objects is weak because their masses

  are small.

Tags

NGSS.MS-PS2-4

NGSS.MS-PS2-5

This diagram shows forces acting on a box. Predict how the box will move (in which direction and with what amount of net force)

• the box will move up with 25 N force

• the box will move left with 100 N force

• the box will move right with 100 N force

• the box will move right with 50 N force

Tags

NGSS.MS-PS2-2

An airplane is traveling at a speed of 200 m/s relative to the Earth. A person walks toward the front of the plane at a speed of 1 m/s. How fast is that person traveling in reference to the other people on the airplane?

• 1 m/s

• 200 m/s

• 201 m/s

• 0 m/s