Physics E1a
Homework Assignment #1 Solutions
Fall 2010
MC 2. The answer is d)
If the car is heading east and slowing down so the positive acceleration must be in
the opposite direction or westward.
MC 3. The answer is a) The magnitude of the average velocity is the change in displacement divided by the
elapsed time.
X
f
!
X
i
"
t
=
0
"
t
=
0
MC 4.
The answer is b)
The average speed is the total distance traveled divided by the elapsed time.
total distance
!
t
=
2
!
y
!
t
MC 17.
The answers are b) velocity does not change with time, a) velocity increases with time at a
constant rate (linear), d) velocity decreases with time at a constant rate (linear), c) velocity increases
with time but at varying rates (non linear).
20.
Strategy
The slope of each segment (between changes in the slope) of the graph is equal to the speed
during that time period.
Solution
Find the speed during each time
period. Then, plot
x
v
as a function of time.
4 m
0
1 s:
4 m s
1 s
x
t
v
<
<
=
=
6 m
4 m
1
3 s:
1 m s
3 s
1 s
x
t
v
!
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 Spring '11
 WolfgangRueckner
 mechanics, Acceleration, Work, Velocity

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