Physics H131: Hints for Problem Set #14

Here are some hints, suggestions, and comments on the problem set:

Chapter N7 Problems

N7S.1: Why is Newton's third law a "red herring" in this case? What is it that determines whether or not your team moves and pulls your opponents' team over? What other forces in addition to the tension forces from the arms and the rope play a role here? Draw free-particle diagrams for the teams and the rope and indicate all forces.
N7S.3: Draw free-particle diagrams of the tug boat and barge, identifying all forces. Write down Newton's second law for both of them. Solve for the forces in question. This is very similar to the pushing of a pair of boxes up an incline which we discussed in class.
N7S.6: Draw a good sketch and free-particle diagram to get started! Use the ideal string and pulley approximations. What do they imply? Which components of Newton's equations are relevant? (Be sure to explain which reference frame(s) you are using!)
N7R.1: This problem is conceptually very close to N7S.1 (see hints above).

N8B.3: How is the magnitude of the lift force related to the weight of the plane? Be sure to look at all the components of Newton's second law! Which way does the acceleration vector point? Where does the acceleration come from?
N8B.4: Which way does the acceleration vector point here (roughly)? What are its components and magnitude?
N8S.7: Draw free-particle diagrams at the top and bottom of the ferris wheel. What are the directions and magnitudes of the relevant forces, and how do they change between the two situations?
N8S.8: Which two forces control the motion of the ball? In which directions do they point? In which direction does the acceleration vector point? How can you check that your final result is correct?
N8S.12: What are the magnitude and directions of the acceleration and force vectors at the top of the loop? Which constraint is provided by the requirement that the car doesn't lose contact with the track? What does this imply for the car's speed at the top of the loop? How is this related to the initial height?

Your comments and suggestions are appreciated.

Physics H131: Hints for Problem Set #14.
Last modified: 08:18 am, October 31, 2008.