| Last revised 1999/08/25 |
11. You might find it useful to plot the graph for part (e) before doing part (b), since you may see the point of part (b) by comparison with part (e). How would a graph of the conditions in part (b) look different? In (b), when does the change in average speed occur? You might find it easier to think about the case where there are two constant speeds in each part. Why does it not matter whether you use constant speeds or average speeds for each interval?
You do not need to know the distance between San Antonio and Houston to work this problem.
12. What is the instantaneous velocity v(t)?
15. How long is it before the trains collide?
To answer the aside
in the text: the bird has a nest on one train and a source of insects
that are food for its young on the other. The insects are really
stupid and the young are really hungry, so it isn't necessary
for the bird to actually stop at either train.
17. It might help to rotate the figure clockwise 90o.
19. No hint unless someone asks me something about the problem.
21. How do you get instantaneous acceleration from v(t)?
23. If v(t) is constant, what does the graph of x(t) look like?
48. If you have any trouble, remember to list all your knowns and unknowns. What is the physics of this situation? Paraphrasing the study guide, "Translate the statement of what the automobile is doing into a statement about physical variables." What formula applies to this physics?
87. Again, what is the physics of this situation? What does the motion of the balloon tell you about the motion of the package? How would the problem differ if the package were thrown downward from the balloon at a speed of 12 m/s relative to the balloon? Remember to list what you know in terms of the variables of a physical problem.
III. Don't forget to include an equation that represents the fact that the two cars are at the same position (along the highway) at a particular time.
| Problem # | Answer |
|---|---|
| 34 | RHW answer: (a) 1.6 m/s (b) 18 m/s |
| 35 | a = (vfinal - v0) / t = 0.28 m/s2 for both the car and the bicycle |
| 36 | RHW answer: (a) 3.1 x 106 sec (b) 4.6 x 1013 m |
| 37 | a = vfinal2 / (2 d ) = 2.78 m/s2 |
| 38 | RHW answer: (a) 0.10 m |