Homework Help: physics

Posted by Ty on Monday, March 24, 2008 at 4:18pm.

questions( there are 3 so I will # 1-3)

info: A 18.9 kg object is attached to a cord that is wrapped around a wheel of radius 10.7 cm. The acceleration of the object down the frictionless incline is measured to be .9 m/s2. Assume the axle of the wheel to be frictionless. The acceleration of gravity is 9.8 m/s2.

1.) Find the tension in the rope. Answer in units of N

2.) Find the moment of inertia of the wheel. Answer in units of kg*m2

3.) Find the angular speed of the wheel 1.77 sec after it begins rotating, starting from rest. Answer in units of rad/sec.

________
so lost! Don't even know where to begin!!!

physics - bobpursley, Monday, March 24, 2008 at 4:41pm
Start with the tension.

T= mg-ma
Then the moment of inertia...

Torque=I *angular acceleration
Force*radius= I * linear acceleration/rad

solve for I.
physics - Ty, Monday, March 24, 2008 at 5:58pm
Found the tension which wasgreat! Thanks.

but would the linear acceleration be .9 m/s2?
physics - Ty, Monday, March 24, 2008 at 6:09pm
never mind- I figured it out.

ok so then, for the angular speed, would I sinply use wfinal ^2=winitial^2+2(angular acceleration)(distance)
?

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