I need help with these three questions please help physics final coming up this week!!!
A disk initially rotatin at 120 rad/ s is slowed down with a constant angular accel of 4 rad/ s^2
1. how long does it take to stop?
2. through what angle does the disk rotate during this time?
3. how many revolutions does it make before stopping?
PLEASE HELP !!!
2007-08-17 07:14:53 · 2 answers · asked by Anonymous in Science & Mathematics ➔ Physics
The principles are the same as linear motion. And this is not an oscillation problem.
α = θ" = - 4
Integrating ω = θ' = -4t + ω0
= -4t + 120
This is zero when t = 30 seconds
Integrating again
θ = -2t^2 + 120*t + 0
When t = 30, θ = 1800 radians
= 1800/(2π) revolutions
= 286.48 revs
2007-08-17 08:25:57 · answer #1 · answered by Dr D 7 · 1⤊ 0⤋
let a = 4 rad/s^2 w0 = 120 rad/s
w = w0-at let w = 0 ---> t = w0/a = 120/4 = 30 sec
let q = angle travelled
q = =1/2a*t^2+w0*t = 1/2*(-4)*900+120 (30) = -1800 +3600 = 1800 rad
number of revolutions = 1800rad/(2*pi) = 900/pi
2007-08-17 14:32:02 · answer #2 · answered by nyphdinmd 7 · 0⤊ 0⤋