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Unformatted text preview: 12.30. Model: The rocket attached to the end of a rigid rod is a rotating rigid body. Assume the rocket is
small compared to 60 cm.
Visualize: Please refer to Figure EX12.30.
Solve: We can determine the rocket’s angular acceleration from the relationship τ = Iα . The torque τ can be
found from the thrust (F) using τ = Fr sin φ . The moment of inertia (I) can be calculated from equations given in
Table 12.2. Specifically, I = I rod about one end + I rocket becomes
M rod L2 + ML2 = (0.100 kg)(0.60 m) 2 + (0.200 kg)(0.60 m) 2
= 0.012 kg m 2 + 0.072 kg m 2 = 0.0840 kg m 2 ⇒α =
I = Fr sin φ (4.0 N)(0.60 m)sin(45°)
= 20 rads/s 2
0.0840 kg m 2 The rocket will accelerate counterclockwise since α is positive. ...
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- Fall '09