Explain each concisely & completely.
1. State the reaction force for each of the following forces:
a: the southward force of a field goal kicker's toe on a football
b: the backward force of a jogger's shoe on the ground
c: the downward force of a book on a desk
d: the backward force of a jet's engines on its exhaust gases
e: the backward pull of a swimmer's hands on the water in the butterfly stroke
2. A beginning physics student, confused by a seeming contradiction in Newton's laws, asks her teacher the following question: "If, for every force there is an equal and opposite reaction force, then all forces in nature come in equal and opposite pairs, and are therefore balanced. Thus, since there can never be such a thing as an unbalanced force, how can any object ever accelerate?" Explain the fault in this common misconception.
3. A fireman at the scene of a fire is holding a heavy hose out of which water is gushing. To keep his balance, he often has to lean. Which way does he lean, forward or backward, and why?
4. A squirrel with an armful of nuts is sliding helplessly across a flat, icy roof, getting dangerously close to the edge. He understands Newton's Third Law, and is able to save himself. Explain how he does it.
5. A clown on roller skates holds a bazooka. Explain what will happen to him (and why) when he fires the bazooka.
6. Two girls, one of mass 40 kg and the other of mass 60 kg, are standing side by side in the middle of a frozen pond. One pushes the other with a force of 360 N for 0.10 s. The ice is essentially frictionless.
a. What is each girl's acceleration? (yes..this is a combination of the 2nd/3rd Laws question)
b. What velocity will each girl acquire in the 0.10 s that the force is acting?
c. How far apart (in cm) will they be during the same time period?
7. In outer space, two astronauts sit at rest next to each other. Bruno, the larger astronaut whose mass is 100 kg, is twice as massive as Timmy, the smaller astronaut. If Bruno pushes Timmy with a force of 100N, how far apart will they be in 2 seconds?
8. A box is sitting at rest on the ground. Does friction act upon this box? Explain using Newton's 2nd Law.
9. Another box is also sitting at rest on the ground. Does it have force pulling it downward due to gravity? Does the box actually accelerate? Explain how your answer must lead (due to Newton's 2nd and 3rd Laws) to another force acting on the box. What direction must this "mystery force" act? (oh, and by the way, we call this force the NORMAL FORCE) Finally, draw a full Free-Body-Diagram (FBD) of this box, which is sitting at rest.