168
Homework Problems
1 . A dinosaur fossil is slowly moving down the slope of a glacier under
the influence of wind, rain and gravity. At the same time, the glacier is
moving relative to the continent underneath. The dashed lines represent
the directions but not the magnitudes of the velocities. Pick a scale, and
use graphical addition of vectors to find the magnitude and the direction
of the fossil's velocity relative to the continent. You will need a ruler and
protractor.
direction of motion
of fossil relative to
glacier, 2.3x10-7 m/s
direction of motion
of glacier relative
to continent, 1.1x10-7 m/s
north
2. Is it possible for a helicopter to have an acceleration due east and a
velocity due west. If so, what would be going on. If not, why not.
3 . A bird is initially flying horizontally east at 21.1 m/s, but one second
later it has changed direction so that it is flying horizontally and 7
°
north
of east, at the same speed. What are the magnitude and direction of its
acceleration vector during that one second time interval. (Assume its
acceleration was roughly constant.)
4. A person of mass M stands in the middle of a tightrope, which is fixed
at the ends to two buildings separated by a horizontal distance L. The rope
sags in the middle, stretching and lengthening the rope slightly. (a) If the
tightrope walker wants the rope to sag vertically by no more than a height
h, find the minimum tension, T, that the rope must be able to withstand
without breaking, in terms of h, g, M, and L. (b) Based on your equation,
explain why it is not possible to get h=0, and give a physical interpretation.
L
h
5. Your hand presses a block of mass m against a wall with a force F
H
acting at an angle
.
. Find the minimum and maximum possible values of
|F
H
| that can keep the block stationary, in terms of m, g,
.
, and
µ
s
, the
coefficient of static friction between the block and the wall.
.
Problem 5.
Chapter 8Vectors and Motion
SA solution is given in the back of the book.A difficult problem.
A computerized answer check is available.
.
A problem that requires calculus.
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