Unit 4 Activity 3 Extension E Quiz
Jan and MIkela are again pulling on the stuffed toy in opposite directions. This time Mikela is pulling with force of 20 N, while Jan is still pulling with a force of 15 N. Which one of the statements below correctly describes the action-reaction partners to these two forces?
B. The toy pulls with a 15 N force on Jan, and a 20 N force on Mikela.
In class you have seen several experiments in which a fan unit was used to exert a force on a low-friction cart, but how is this force generated? When a fan is made to turn, the shapes of the blades are such that they push the air they come in contact with away from them. (That is how they create a breeze!) If the fan blades push the air in one direction away from them, what effect does this have on the fan blades themselves?
C. The air exerts a force on the fan blades in the direction opposite to the direction in which the air is pushed.
Imagine you try to push a heavy box across the floor using a force of 150 N. Even with this strength push, it does not start to move. Which one of the following best explains why the box does not start to move under these circumstances?
C. There must be some other object, such as the floor, pushing in the opposite direction on the box with a force that also has a strength of 150 N, thereby making the forces acting on the box balanced.
A boy holding a large snowball is standing at rest on ice skates in the middle of a frozen pond. He throws a snowball at his friend on the shore and notices that, as he does so, he begins to move slowly in the direction opposite to his throw. A student writes the following explanation for why the boy starts to move in the direction opposite to that in which he throws the snowball. He begins by drawing separate force diagrams (to the right) for the boy and the snowball for the time when the boy is throwing the snowball, before it leaves his hand. What is your evaluation of the force diagram and the explanation?
D. Both the diagrams and the narrative are good.