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Chapter 2, Motion in One Dimension
C
HAPTER
2
Conceptual Problems
C1. A ball of relatively low density is thrown upwards. Because of air resistance the acceleration
while traveling upwards is –10.8 m/s
2
. On its trip downward the resistance is in the opposite
direction and the resulting acceleration is –8.8 m/s
2
. When the ball reaches the level from
which it was thrown, how does its speed compare to that with which it was thrown?
a. It is greater than the original speed upward.
b. It is the same as the original speed upward.
c. It is less than the original speed upward.
d. Without knowing the original speed, this problem cannot be solved.
C2. Starting from rest, a car accelerates down a straight road with constant acceleration
a
1
for a
time
t
1
, then the acceleration is changed to a different constant value
a
2
for an additional time
t
2
. The total elapsed
time is
t
1
+
t
2
. Can the equations of kinematics be used to find the total
distance traveled?
a. No, because this is not a case of constant acceleration.
b. Yes, use (
a
1
+
a
2
)/2 as the average acceleration and the total time in the calculation.
c. Yes, use
a
1
+
a
2
as the acceleration and the average time (
t
1
+
t
2
)/2 in the calculation.
d. Yes, break the problem up into 2 problems, one with the conditions for the first
time interval and the other with the conditions for the second time interval, noting that
for the second time interval the initial velocity is that from the end of the first time
interval. When done, add the distances from each of the time intervals.
C3. Starting from rest, a car accelerates down a straight road with constant acceleration
a
for a
time
t
, then the direction of the acceleration is reversed, i.e., it is –
a
, and the car comes to a
stop in an additional time
t
, the time for the whole trip being 2
t
. At what time, or times, is the
average velocity of the car for the trip equal to its instantaneous velocity during the trip?
a. There is no such time.
b. It is at the halfway point at
t
.
c. This occurs at 2 times, 0.5
t
and 1.5
t
.
d. This occurs at 2 times, 0.707
t
and 1.293
t
.
C4. A ball rolls down an incline, starting from rest. If the total time it takes to reach the end of the
incline is T, how much time has elapsed when it is halfway down the incline?
a. 0.5 T
b. < 0.5 T
c. > 0.5 T
d. More information is needed.
13
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C5. In which of the following cases is the displacement’s magnitude half the distance traveled?
a. 10 steps east followed by 3 steps west
b. 22 steps east followed by 11 steps west
c. 5 steps east followed by 10 steps west
d. 15 steps east followed by 5 steps west
2.1 Displacement
1.
A change in a physical quantity
w
having initial value
w
i
and final value
w
f
is given by which
of the following?
a.
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This note was uploaded on 01/06/2012 for the course PHYS 201 taught by Professor Coffin during the Spring '09 term at Oregon State.
 Spring '09
 COFFIN
 Resistance, Acceleration

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