Calculations are to be done to 5 significant places.
All work must be shown.
1.
An auto travels at the rate of 25 km/h for 4.0 minutes, then at 50km/h for 8.0 minutes and
finally at 20 km/h for 2.0 minutes.
Find, a. the total distance covered in km and, b. the
average speed for the complete trip in m/s.
1
4.0 min
4.0 min
0.066667
60 min
h
h
=
=
1
8.0 min
8.0 min
0.13333
60 min
h
h
=
=
1
2.0 min
2.0 min
0.033333
60 min
h
h
=
=
(a) The distance traveled is
25
(0.066667
)
50
(0.13333
)
20
(0.033333
)
8.9998
km
km
km
d
h
h
h
h
h
h
km
=
+
+
=
(b) The total time is
t = 4.0
min + 8.0 min + 2.0 = 14.0 min
The average speed is
8.9998
8999.8
8999.8
10.714
14.0 min
14.0(60 s)
840.0 s
d
km
m
m
m
v
t
s
=
=
=
=
=
2.
Starting from the center of town, a car travels east for 80.0 km and then turns due south for
another 192 km, at which point it runs out of gas.
Determine the displacement of the
stopped car from the center of town.
By Pythagorean Theorem the displacement is
2
2
d
a
b
=
+
2
2
2
2
2
(80.0
)
(192
)
6400
36864
43264
208
d
km
km
km
km
km
km
=
+
=
+
=
=
192
tan
2.4
80.0
θ
=
=
1
0
tan
2.4
67.380
θ

=
=
south of east
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3.
A bug starts at point A, crawls 8.0 cm east, then 5.0 cm south, 3.0 cm west, and 4.0 cm
north to point B. (A) how far north and east is B from A? (B) Find the displacement from A
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 Winter '11
 Landen
 Physics, Pythagorean Theorem, Work, Velocity

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