Physics 130
Exam 1
Short Answer.
Please answer all of the short answer questions.
1.
A new group is trying to shatter the land speed record.
Their goal is to go 1000 mi/hr.
How
fast is this in m/s?
v
=
1000
mi
hr
⋅
1600
km
1
mi
⋅
1
hr
3600
s
=
444.4
m
/
s
2.
You have a leaky faucet.
If it drips once per second, estimate how what volume water you
will have wasted in 1 year.
If the density of water is 1000 kg/m
3
, what mass of water is this?
Estimated that each droplet is 1/8 cm
3
.
V
=
1/ 8
cm
3
s
⋅
3600
s
1
hr
⋅
24
hrs
1
day
⋅
365
days
1
yr
⋅
1
yr
=
3.94
×
10
6
cm
3
=
3.94
×
10
6
cm
3
⋅
1
m
100
cm
⎛
⎝
⎜
⎞
⎠
⎟
3
=
3.94
m
3
m
=
1000
kg
m
3
⋅
3.94
m
3
=
3940
kg
3.
If the vehicle that is attempting to break the land speed record by reaching 1000 mi/hr
achieves a constant acceleration of 1.5 g’s, how long will it take to reach its design speed of 1000
mi/hr?
Assume it started from rest.
x
i
=
0
x
f
=
?
v
i
=
0
m
/
s
v
f
=
444.4
m
/
s
a
=
1.5
g
t
=
?
v
f
=
v
i
+
at
v
f
=
0
+
1.5
gt
t
=
v
f
1.5
g
=
444.4
m
/
s
1.5
⋅
9.8
m
/
s
2
=
30.23
s
4.
How far will you need to
stop
your vehicle if it is going 1000 mi/hr?
Assume that the vehicle
can decelerate with magnitude 0.5 g.
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x
i
=
0
x
f
=
?
v
i
=
444.4
m
/
s
v
f
=
0
m
/
s
a
=
−
0.5
g
t
=
?
v
f
2
=
v
i
2
+
2
a
(
x
f
−
x
i
)
0
=
v
i
2
+
2(
−
0.5
g
)(
x
f
−
0)
x
f
=
v
i
2
2(0.5
g
)
=
20,152.2
m
5.
The position of a particle is given by
x
(
t
)
=
2
+
5
t
2
+
10
t
3
Find the average velocity over the interval 0 s to 2 s, the instantaneous velocity at 1s, and the
instantaneous acceleration at 1s.
x
(
t
)
=
2
+
5
t
2
+
10
t
3
x
(0)
=
2
m
x
(2)
=
102
m
v
avg
=
x
(2)
−
x
(0)
2
s
=
50
m
/
s
x
(
t
)
=
2
+
5
t
2
+
10
t
3
v
(
t
)
=
10
t
+
30
t
2
v
(1)
=
40
m
/
s
6.
Consider vectors
a
=
4
ˆ
i
+
−
3
ˆ
j
and
b
=
13
ˆ
i
+
5
ˆ
j
Compute the magnitude and direction of
BOTH
a
and
b
.
Compute the result of
a
−
b
,
a
⋅
b
,
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 Spring '10
 jojo
 Acceleration, Velocity, land speed record, Oquawka

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