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9. (a) Translate the following information into symbols, using the notation
with two subscripts introduced in section 2.5. Eowyn is riding on her horse
at a velocity of 11 m/s. She twists around in her saddle and fires an arrow
backward. Her bow fires arrows at 25 m/s. (b) Find the speed of the arrow
relative to the ground.
10 S. Our full discussion of two- and three-dimensional motion is post-
poned until the second half of the book, but here is a chance to use a little
mathematical creativity in anticipation of that generalization. Suppose a
ship is sailing east at a certain speed v, and a passenger is walking across the
deck at the same speed v, so that his track across the deck is perpendicular
to the ship’s center-line. What is his speed relative to the water, and in what
direction is he moving relative to the water.
11
.
. Freddi Fish
(TM)
has a position as a function of time given by
x=a/(b+t
2
). Find her maximum speed.
12. Driving along in your car, you take your foot off the gas, and your
speedometer shows a reduction in speed. Describe a frame of reference in
which your car was speeding up during that same period of time. (The frame
of reference should be defined by an observer who, although perhaps in
motion relative to the earth, is not changing her own speed or direction of
motion.)
Homework Problems