Crossing the River II. (a) In which direction should the motorboat in Exercise 3.35 head to reach a point on the opposite bank directly east from your starting point? (The boat’s speed relative to the water remains 4.2 m/s.) (b) What is the velocity of the boat relative to the earth? (c) How much time is required to cross the river?
Crossing the River II. (a) In which direction should the motorboat in Exercise 3.35 head to reach a point on the opposite bank directly east from your starting point? (The boat’s speed relative to the water remains 4.2 m/s.) (b) What is the velocity of the boat relative to the earth? (c) How much time is required to cross the river?
Crossing the River II. (a) In which direction should the motorboat in Exercise 3.35 head to reach a point on the opposite bank directly east from your starting point? (The boat’s speed relative to the water remains 4.2 m/s.) (b) What is the velocity of the boat relative to the earth? (c) How much time is required to cross the river?
A fish swims directly east across a river, but
it is pulled 672m downstream (south) by a
strong 6.00 m/s current. The fish was going
at its maximum speed of 4.0 m/s(relative to
the water) directly across the river.
a) How wide is the river?
b) How long does it take the fish to cross
the river?
c) What was the fish's speed relative to the
shore?
d) What is the angle of the resultant vector?
e) A fish swims directly across a river, but it's
pulled by a strong current. If the river
current doubled, then the time required for
the fish to reach the opposite shore would
be : one quarter, one half, doubled, the
same?
In a circus, a “human cannonball” is launched from a cannon and lands in a net. The cannon releases him at the same height as the net. His initial velocity is 18.3 m/s in a direction 40.0° above the horizontal.
a) For how much time will he be in the air?
b) How far does he travel horizontally?
c) What is the velocity upon impact?
The circus manager from the previous question wants to make the stunt more dramatic by firing the stuntman through a hoop 9.0 m high then land in a safety net at the same height as the cannon. The cannon’s angle is changed to 45.0° and the velocity is increased to 21.0 m/s. The manager needs to know where to place the hoop and safety net.
a) How far from the cannon should the safety net be placed?
b) What is the time required to reach the height of the hoop?
c) How far from the cannon should the hoop be placed?
3. A student can row a boat 6km/h in still waters, she is on one bank of a 6
km wide river that has current of 3km/h.
A. assuming she is allowed to land anywhere on the shore:
(i) What is the smallest amount of time she needs to get to the opposite
bank?
(ii) What is the student's speed as viewed by the observer on the bank?
B. If the student has to land on the opposite bank at the point exactly
across from where she starts:
(iii) What angle should her boat make with respect to a line running
straight the river?
(iv) What is the student's speed as viewed by the observer on the bank of
the river?
(v) How much time would she need to cross the river
Chapter 3 Solutions
University Physics with Modern Physics, Volume 2 (Chs. 21-37); Mastering Physics with Pearson eText -- ValuePack Access Card (14th Edition)
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