First Midterm for Phys.161
Spring, 2008
March 5
Closed Book
Time: 50 min.
Dr. R. N. Mohapatra
Problem 1.
You are standing on the ground at the origin of a coordinate system. An airplane
flies over you with a constant velocity and at a constant height of 7600 m above you
at
t
= 0.
(i) Denoting the height above you as the yaxis, what is the position vector
vector
P
0
of
the plane in vector notation at
t
= 0 ? Use
i
and
j
as unit vectors along the x and
ydirection. [5]
(ii) At
t
= 30
.
0, the position vector is given by
vector
P
30
= 8400
i
+ 7600
j
. Write down
the vector representing the plane’s velocity . [10]
(iii) Determine the plane’s position in vector notation at
t
= 45 sec. . What is
the angle between the plane’s position vector and bthe yaxis at
t
= 45 sec.? [10]
(iv) If instead of remaining standing on the ground, you are in a car going at
30m/s along the negative xdirection, what would be the velocity measured in the
moving car ? [5]
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Problem 2.
A placekicker must kick a football from a point 36.0 m from the goal and the
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 Fall '09
 Mohapatra
 mechanics, Vectors, Acceleration, Velocity, Euclidean geometry

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