A wagon wheel is made of an outer rim and several rod shaped spokes. The rim is
ID: 2244980 • Letter: A
Question
A wagon wheel is made of an outer rim and several rod shaped spokes. The rim is a ring with a mass of 5.20 kg and a radius of 0.600m.Attached to the wheel are 12 rods attached to the rim of the wheel and the center, each with a length equal to the radius of the wheel and a mass of 0.450 kg. The wheel rolls without slipping on a horizontal upper level floor as shown in the figure. The wheel rolls to the right with an initial velocity of 0.550m/s, 1.00 m above the lower level.(A)Set up the integral for calculating the moment of inertial for the rim of the wheel.You do not need to solve it.(B)The wheel rolls down a ramp.What is the wheel's speed on the lower level.
Explanation / Answer
a)
let m1 + m2 = M = 5.65 kg
I_ring = m1*R^2
I_rod = m2*R^2/3
total moment of inertia ofsystem,
I = I_ring + 12*I_rod
= m1*R^2 + 12*m2*R^2/3
= (3*m1*R^2+12*m2*R^2)/3
= 5*(m1+m2)*R^2
= 5*M*R^2
b)
accrdoing to conservation of enrgy
0.5*M*v1^2 + 0.5*I*w1^2 + m*g*h = 0.5*M*v2^2 + 0.5*I*w2^2
0.5*M*v1^2 + 0.5*5*M*R^2*w1^2 + m*g*h = 0.5*M*v2^2 + 0.5*5*M*R^2*w2^2
0.5*M*v1^2 + 2.5*M*v1^2 +m*g*h = 0.5*M*v2^2 + 2.5*M*v2^2
3*M*v1^2 + M*g*h = 3*M*v2^2
v2^2 = v1^2 + g*h/3
v2 = sqrt(v1^2 + g*h/3)
= sqrt(0.55^2 + 9.8*1/3)
= 1.889 m/s
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