Angular Momentum of a Tire (Help)

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The discussion revolves around calculating the change in angular momentum of a tire rolled by a boy, with specific parameters provided, including mass, radius, and moment of inertia. The boy pushes the tire at a speed of 2.1 m/s while it leans at a 10° angle. The attempted solution involves calculating angular velocity and angular momentum, but confusion arises regarding the comparison of torque's effect over time. The response highlights the complexity of the problem and points out that torque is not measured in seconds, indicating a misunderstanding in the approach. Clarification on the relationship between torque and angular momentum is needed for a correct solution.
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Problem:
A boy rolls a tire along a straight level street. The tire has mass 8.0 kg, radius 0.34 m and moment of inertia about its central axis of symmetry of 0.83 kg·m2. The boy pushes the tire forward away from him at a speed of 2.1 m/s and sees that the tire leans 10° to the right

Compare the change in angular momentum caused by this torque in 0.20 s to the original magnitude of angular momentum.
(change in momentum / original magnitude of angular momentum)

Relevant formulas:
L = Iw
v = Rw
L = rpsin(theta)

Attempted Solution:
w = 2.1m/s / .34 m = 6.176
L = Iw = (.83)(6.176) = 5.126

r = .2*2.1 = .42m
p = (8kg)(2.1)= 16.8
.42*16.8*sin(10) = 1.225

1.225/5.126 = .239

I was wondering if you could tell me what I'm doing wrong and walk me through the right process.

Thanks
 
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Moved to Homework Help forums.

Woof. Not a simple problem. But this makes it overly hard/obscure:

"Compare the change in angular momentum caused by this torque in 0.20 s to the original magnitude of angular momentum."

The units of torque are not seconds...
 
Last edited:
Welcome to the PF, BTW!
 
The book claims the answer is that all the magnitudes are the same because "the gravitational force on the penguin is the same". I'm having trouble understanding this. I thought the buoyant force was equal to the weight of the fluid displaced. Weight depends on mass which depends on density. Therefore, due to the differing densities the buoyant force will be different in each case? Is this incorrect?

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