PHYSICS ASAP?!(11/12/13)?

Question

a.) A cable passes over a pulley. Because the
cable grips the pulley and the pulley has nonzero mass, the tension in the cable is not the
same on opposite sides of the pulley. The
force on one side is 138 N, and the force on
the other side is 79 N.
Assuming that the pulley is a uniform disk
of mass 2.68 kg and radius 1.113 m, find the
magnitude of its angular acceleration. [For a
uniform disk, I = (1/2)mr2]
Answer in units of rad/s2

b.) The wheel on an upside-down bicycle moves
through 17.9 rad in 5.72 s.
What is the wheel’s angular acceleration if
its initial angular speed is 1.5 rad/s?
Answer in units of rad/s2

c.) The net work done in accelerating a propeller
from rest to an angular speed of 260 rad/s is
1061.0 J.
What is the moment of inertia of the propeller?
Answer in units of kg · m2

Andrew Smith · Answer

Torque /moment of inertia = dw/dt
Torque = net force * radius = 59*r
-> dw/dt = 59*r /( 1/2 m r^2) = 59 *2 /(mr)= 39.6 rad/s^2
b) s= ut + 1/2 a t^2 -> s-ut = 1/2 a t^2 ->2(s-ut)/ t^2 = a { which is dw/dt}
=2*(17.9-1.5*5.72)/ 5.72^2 =0.570 rad/s^2

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PHYSICS ASAP?!(11/12/13)?

1 Answer