ss The three 150 g masses in the figure (Figure 1) are connected by massless, ri
ID: 1488233 • Letter: S
Question
ss
The three 150 g masses in the figure (Figure 1) are connected by massless, rigid rods.
Part A
What is the triangle’s moment of inertia about the axis through the center?
Express your answer to two significant figures and include the appropriate units.
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Part B
What is the triangle’s kinetic energy if it rotates about the axis at 5.0 rev/s ?
Express your answer to two significant figures and include the appropriate units.
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The three 150 g masses in the figure (Figure 1) are connected by massless, rigid rods.
Part A
What is the triangle’s moment of inertia about the axis through the center?
Express your answer to two significant figures and include the appropriate units.
Explanation / Answer
a = side of triangle = 40 cm = 0.40 m
r = distance of each mass from axis of rotation = a/sqrt(3) = 0.40 / sqrt(3) = 0.231 m
m = mass at each vertex = 150 g = 0.15 kg
Total moment of inertia is given as
I = 3 mr2 = 3 (0.15) (0.231)2 = 0.024 kgm2
b)
W= 5 rev/s = 5 x 2 x 3.14 rad/s = 31.4 rad/s
Rotational KE is given as
RKE = (0.5) I W2 = (0.5) (0.024) (31.4)2 = 11.83 J = 1.2 x 101 J
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