Chapter 3 problems
1B 
Both balls hit the groupd at the same time because the horizontal and vertical motions are
independent. The red ball has the higher speed because it has an additional horizontal component of
velocity while its vertical velocity is the same as the blue ball
2C  The x component of the velocity remains the same, and the acceleration is always g.
3D  The magnitude of the resultant vector has to be smaller than 240 (200+40) and larger than 160(200
40).
21B 
By definition, the average velocity is the displacement (2 radii = 60.0 m east) divided by the time
duration (30.0s).
22D 
By definition, the average speed is the distance (for a half circle:
r) divided by the time duration.
25E  Average acceleration= total velocity change/total time interval. Total velocity change is 3.14m/s * 2
because we go from 3.14 m/s due north to 3.14 m/s due south.
Then we have acceleration = 2*3.14 m/s/30.0s= 0.209 m/s
2
27C 
V
f
=V
i
+at= 30 m/s 3.00m/s
2
* 4.00s=18.0 m/s, West
28C 
Vsouth= 3.00m/s
2
*4.00s = 12.0m/s
Vwest = 30m/s
V
2
=(12.0m/s)
2
+(30m/s)
2
= 1044 m/s
2
; V = 32.3
m/s, tan(angle) = 12/30, therefore angle = 21.8 degrees (
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 Fall '09
 ZHIXIANZHOU,
 Velocity, 60.0 m, 20m/s, 91 m, 50m/s, 15.3m

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