1. Newton's Third Law.
a. A very smart three year old child is given a wagon for her birthday. She refuses to use it. "After all," she says, "Newton's third law says that no matter how hard I pull, the wagon will exert an equal but opposite force on me. So I will never be able to get it to move forward." What would you say to her in reply? Draw frpgftwty diagrams of the girl and the wagon to support your answer.
[FOR PART B REFER TO THE SCREENSHOT ON THE BOTTOM OF THE PAGE]
b. Use the setup in warmup problem 6b (screenshot below). The mass of the penguin is 5.0 kg and the mass of the sled is 10.0 kg. The coefficient of kinetic friction between all surfaces is 0.20 and the coefficient of static friction between all surfaces is 0.30.
i. Draw the force diagrams for the penguin and the sled. Identify all of the Newton's third law pairs.
ii. What is the tension in the rope that connects the penguin and the post?
iii. What is the acceleration of the sled?
2. A penguin is on a sled as shown in the image. A force of 45 N is applied to the sled, but although the sled moves to the right, the penguin remains stationary (with respect to the ground) due to his connection with a cord tied to a post. In other
words, the penguin does not move in the horizontal direction; the sled slides out from underneath him. There is friction between all surfaces. Draw the free-body diagrams for the penguin, the sled, the pole, and the ground.
