AJM:12/14/01 Score /100
Physics 131 Midterm Winter 1998
Name
Please work the problems on separate sheets of paper and staple this sheet to the front. Read each problem
carefully. Show your work and/or give explanations for all answers. Make sure that your answers are
given with a reasonable number of sig figs and that you have included appropriate units. Check your
answers for physical reasonableness whenever possible. I do give partial credit, but only if I can follow
your work, so be as clear as possible about what you are doing.
1. [25 pts] On Planet X freely falling objects have a constant acceleration of 5.0 m/s2. When a baseball is
thrown directly upward from the surface of the planet with an initial speed of 30 m/s, what is the
maximum height that it reaches? (Neglect air resistance.)
2. [25 pts] Starting from home, a woman walks 2.0 km west. Then she turns to a
direction 30° to the east of south and walks 3.0 km. Finally she walks 4.0 km north.
a) How far is she from home?
b) What direction should she walk to go directly home?
3. A rock is thrown horizontally off the edge of a vertical cliff with an initial speed of 24
m/s. It hits level ground extending away from the base of the cliff 4.0 s later.
a) [5 pts] How far from the base of the cliff does the rock land? (Please neglect air resistance.)
b) [10 pts] How high is the cliff?
c) [10 pts, harder] If the rock had been thrown with the same speed but at an angle 30° above the
horizontal, how far from the base of the cliff would it have landed?
4. A man drags a 30 kg suitcase along level ground at a constant speed
using a strap attached to the suitcase that makes a 25° angle with the
horizontal as shown at right. The coefficient of kinetic friction between
the suitcase and the ground is 0.45.
a) [15 pts] How hard does the man have to pull—i.e., what is the
tension in the strap? [A simple reminder: “Use the method!”]
b) [10 pts] If the man pulled just as hard on the moving suitcase (as in
part a), but with the strap horizontal instead of at a 25° angle, would
the suitcase speed up or slow down? (As always, show your calculations; no credit for simply
guessing correctly!)
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