Electromagnetism

A student pushes a cart against a wall exerting 500 N of force. The cart doesn't move. a. How do you explain what happened? (Mark the one best answer.)

• A The wall pushes back with 1,000 N of force.
• B The wall pushes back with 250 N of force.
• C The wall pushes back with 500 N of force.
• D Walls are stationary; they can't push or pull.

What can you say about the forces?

• F The net force is 0 because the cart is not moving.
• G The net force is greater than 0 because the wall could push back more.
• H There is no net force because a wall can’t push or pull.
• J The net force is less than 0 because the person is pushing on the wall.

. Team A pulls on a rope in a game of tug-of-war with 1,800 N of force. Team B pulls on the other side of the rope. In between the teams is a mud pit. How much force does Team B need to use in order to pull Team A into the mud?

(a)  

Three young children are fighting over where to take Super Dog. Child X pulls the wagon, trying to go in the direction of his house. Child Y pushes on the wagon toward the same house. Child Z pushes on the wagon, trying to move it in the opposite direction. The forces from the three children being exerted on the wagon are 300 N, 500 N, and 200 N (not necessarily in XYZ order). If the wagon isn’t moving, how much force is Child Z exerting on the wagon? (Mark the one best answer.)

• A There is not enough information to determine Child Z’s force.
• B 200 N
• C 300 N
• D 500 N

In order to move a carton of books across table A, a student had to push with 15 N of force. In order to move a carton of books with the same mass across table B, the student had to push with 25 N of force. Which table has a smoother surface?

• Table A
• Table B

Aristotle had ideas developed from thought experiments about force that people believed for more than 2,000 years. In the 1600s, Galileo conducted investigations with objects and presented new ideas about force. Which great thinker had better evidence to support his claims? (Mark the one best answer.)

• ❍ A Aristotle, because he was the  rst to describe the motion of objects
• ❍ B Aristotle, because he used thought experiments to support his ideas
• ❍ C Galileo, because he used ball-and-ramp experiments to support his ideas
• ❍ D Galileo, because he was a scientist rather than a philosopher

A baby rhino runs playfully at his mother and bumps into her. The baby falls backward from the impact.

• Newton's first law of motion
• Newton's second law of motion
• Newton's third law of motion

A fish swimming through water pushes water backwards with its fins. The water propels the fish forward.

• Newton's first law of motion
• Newton's second law of motion
• Newton's third law of motion

The following measurement describes this type of motion: 951 N

• acceleration
• force
• speed

Mass varies depending on where the object is located. _______________

• True
• False