Electro
Nov13-04, 03:48 PM
Hello,
I have a problem dealing with torques and acceleration. I am sure I solved it right but when submitting the answers, I get the response "Incorrect" :cry:
The problem:
A wheel of radius 2 m, mass 53 kg, and moment of inertia (3/4) (53 kg) (2m)^2 about the center of mass is mounted on a frictionless horizontal axle.
(g = 9.8). A light cord wrapped around the wheel supports an object of mass 106 kg. The weight is released from rest at the level of A and falls a distance h, past level B (AB=28 m). a) Find the velocity as it passes B b) Determine the tension of the string.
I set up everything.
Torque = I* alpha = T*R since alpha = a/R and we know I, conclusion is T=42*a
Then: T=m(g - a): putting T from above, I got a=7.0189189 m/s^2
To find V as the mass passes point B: Vf^2 = 2*a*28m ---> and v at B = 19.83 m/s. This was OK
For b) I used T=m(g-a), since I know a = 7.0189189m/s^2 , I substituted it at the equation and I got T= 294.79 N but this is not the right answer.
Maybe I can use I*alpha = T*R and from that get T because everything is known, but I am not sure. Any suggestions?
I have a problem dealing with torques and acceleration. I am sure I solved it right but when submitting the answers, I get the response "Incorrect" :cry:
The problem:
A wheel of radius 2 m, mass 53 kg, and moment of inertia (3/4) (53 kg) (2m)^2 about the center of mass is mounted on a frictionless horizontal axle.
(g = 9.8). A light cord wrapped around the wheel supports an object of mass 106 kg. The weight is released from rest at the level of A and falls a distance h, past level B (AB=28 m). a) Find the velocity as it passes B b) Determine the tension of the string.
I set up everything.
Torque = I* alpha = T*R since alpha = a/R and we know I, conclusion is T=42*a
Then: T=m(g - a): putting T from above, I got a=7.0189189 m/s^2
To find V as the mass passes point B: Vf^2 = 2*a*28m ---> and v at B = 19.83 m/s. This was OK
For b) I used T=m(g-a), since I know a = 7.0189189m/s^2 , I substituted it at the equation and I got T= 294.79 N but this is not the right answer.
Maybe I can use I*alpha = T*R and from that get T because everything is known, but I am not sure. Any suggestions?