- #1
jaredsees
- 2
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1. Homework Statement
Two pulley wheels, one of radius 0.5m and the
other of radius 1.75 m, are mounted rigidly on
a common axle. The rotational inertia of the
two pulleys, which are clamped together, is
1.5 kg*m2. A mass of 7.5 kg mass is attached
on the left and a mass of 5.5 kg mass on the
right, as shown.
Here is the image: http://yfrog.com/jwpulleyp
a.) Find the angular acceleration of the system. Take clockwise direction to be positive. Units in rad/s^2
b.) Find the tension in the cord attached to the 7.5 kg mass (units in N)
c.) Find the tension in the cord attached to the 5.5 kg mass (units in N)
2. Homework Equations
net torque = I * a
3. The Attempt at a Solution
Torque = I * a
Torque = m2*g*r2 - m1*g*r1
torque = 5.5*9.8*1.75 - 7.5*9.8*.5
= 57.58
a = Torque / I
=> 57.58 / 1.5 =38.39 rad/s2
Tried to submit the answer, but it was wrong. Don't know what I am doing wrong in part A. And I'm not sure how to do attempt Part b or c. Any advice appreciated!
Two pulley wheels, one of radius 0.5m and the
other of radius 1.75 m, are mounted rigidly on
a common axle. The rotational inertia of the
two pulleys, which are clamped together, is
1.5 kg*m2. A mass of 7.5 kg mass is attached
on the left and a mass of 5.5 kg mass on the
right, as shown.
Here is the image: http://yfrog.com/jwpulleyp
a.) Find the angular acceleration of the system. Take clockwise direction to be positive. Units in rad/s^2
b.) Find the tension in the cord attached to the 7.5 kg mass (units in N)
c.) Find the tension in the cord attached to the 5.5 kg mass (units in N)
2. Homework Equations
net torque = I * a
3. The Attempt at a Solution
Torque = I * a
Torque = m2*g*r2 - m1*g*r1
torque = 5.5*9.8*1.75 - 7.5*9.8*.5
= 57.58
a = Torque / I
=> 57.58 / 1.5 =38.39 rad/s2
Tried to submit the answer, but it was wrong. Don't know what I am doing wrong in part A. And I'm not sure how to do attempt Part b or c. Any advice appreciated!
)
… don't the two masses have angular momentum also? 
