A wheel with rotational inertia I is mounted on a fixed, fricitonless axle. The angular speed w of the wheel is inccreased from zero to w_f in a time interval T.
1: What is the average net torque on the wheel during the time interval, T?
a) w_f/T
b)w_f/T^2
c) Iw_f^2/T
d)Iw_f/T^2
e)Iw_f/T
I know that torque equals rFsin theda and r=sqrt(I/m). Is the answer e)?
2: What is the average power input to the wheel during this time ineterval T?
a) Iw_f/2T
b_Iw_f^2/2T
c)Iw_f^2/2T^2
d)I^2w_f/2T^2
e)I^2w_f^2/2t^2
what is the equation for power? I don't get this part of the problem... If i had to guess would the answer be b)?
Your reasoning on 1 baffles me. What is avg angular acceleration: wf/T.
Torque= I *angular acceleration
Power? Work= Torque*angular displacement
but angular displacement= 1/2 angacc*time^2
Power= work/time= I*wf/T*1/2*wf/T*T
work it out, and check that.
My girl Teresa out here responding 9 years later
okay so P=W/t
so the force is the torque from the first problem and you need to find the d
ang. acc. = wf/t
so you use that to plug into the formula: wf^2= wi + 2(alpha)(d)
change wi to zero
and substitue wf/t into alpha and solve for d
use that as the d for Fxd/T and you'll get
Iwf^2/T2