Practice Problems 7
1
. Three masses are connected by massless rigid rods. Rods AC and CB have length
l
=
12.1 cm. If
m
A
=141.0 g,
m
B
=205.0 g, and
m
C
=311.0 g, what are the coordinates of the
center of mass?
Answer:
9.50e02 m 3.78e02 m
(
x
coordinate first, followed by the
y
coordinate.)
2
. A 3.50 m long rigid beam with a mass of 110.0 kg is supported at each end. A 84.4 kg
student stands 1.64 m from support 1. How much upward force does each support exert
on the beam? (Enter your answer for support 1 first, followed by your answer for support
2.)
Answer:
9.80e+02 N 9.28e+02 N
3
. A 3.42 m long ladder leans against a frictionless wall. The coefficient of static frictin
between the ladder and the floor is 0.440. What is the minimum angle, in radians, that the
ladder can make with the floor without slipping?
Answer:
8.49e01 rad
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. A baseball player holds a 37.8oz bat (weight = 10.5 N) with one hand at the point
0
as
shown in the figure below.
The bat is in equilibrium. The weight of the bat acts along a line
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 Spring '08
 N. MCKAY
 mechanics, Center Of Mass, Force, Mass, 5.95 m, 2.20 m, 3.75 m, 3.50 m, 3.42 m

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