A 1.0 kg light is swung at the end of a string in a horizontal circle of radius 1.0 m with a constant angular speed. If no torque is applied, what must the radius become if the angular speed of the flashlight is to be doubled?
2006-08-08 08:19:45 · 2 answers · asked by todd b 1 in Science & Mathematics ➔ Physics
a. 1.0 m
b. .72 m
c. 1.5 m
d. 1.3 m
2006-08-08 08:49:10 · update #1
I'm not sure you're giving the whole story. I'm assuming you mean the angular momentum stays constant since there's no torque applied.
H = Iw ; where H (angular momentum) equals I (moment of inertia) times w (angular velocity).
The key is that the moment of inertia decreases when you decrease the radius.
I = mr^2 where I (moment of inertia) equals mass times the radius squared.
Working backwards, if the angular velocity is doubled, the moment of inertia has to be half its original value. The mass is unlikely to change, so the radius has to change by the sqrt (1/2).
1 * sqrt(1/2) = .707
2006-08-08 08:46:54 · answer #1 · answered by Bob G 6 · 0⤊ 0⤋
Do your own homework. Find the equation that relates angular speed to radius and double the speed. These are simple problems.
2006-08-08 09:08:47 · answer #2 · answered by Davon 2 · 0⤊ 0⤋