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).
Chapter N8 Problems
- 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.
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Physics H131: Hints for Problem Set #14.
Last modified: 08:18 am, October 31, 2008.
furnstah@mps.ohio-state.edu