Problem finding angular velocity

AI Thread Summary
The discussion focuses on calculating the angular velocity of a uniform disk subjected to a constant downward force. The disk, which weighs 9.65 lb and has a radius of 0.470 ft, is pinned at its center and starts from rest. The user initially struggled to relate the applied force to angular acceleration, using the equation involving torque and moment of inertia. After several attempts and two days of work, the user resolved the issue by identifying numerical errors in their calculations. The problem was ultimately solved, confirming the correct approach to finding angular velocity.
Coletrain12
Messages
16
Reaction score
0
[SOLVED] Problem finding angular velocity... !

Homework Statement




The 9.65 lb uniform disk is pin supported at its center and is acted upon by a constant force of P = 1.45 lb as shown. The system starts from rest. Radius of disk is .470 ft

The force P is going straight down from the disk and would spin the disk in a clockwise direction. The force P is at the end of a string.. making the disk spin.

Determine the angular velocity after 4.45 seconds. (rad/s, +CCW)

Homework Equations



I know this problem involves a constant accel equation. I believe the right one is angvelfinal = angvelinitial + a*t



The Attempt at a Solution



The issue i have is that i can't figure out how to relate the force acting on the disk to turn it into acceleration. I have tried setting "Force*Radius=(.5*Mass*radius^2)angaccel" and solving for angaccel and then multiplying it by the time in order to get my angvel but i am having no luck. Any help i appreciated.
 
Physics news on Phys.org
any other info i need to give guys?? i have been on this question for two days lol. I can finish it i just can't figure out how i get from a force in lbs pulling down on a string turning a disc... to the acceleration of the disc. I've looked through formulas and have had no luck anywhere.
 
thanks guys, i figured it out. I was doing it right but somehow my numbers were off somewhere.
 
Kindly see the attached pdf. My attempt to solve it, is in it. I'm wondering if my solution is right. My idea is this: At any point of time, the ball may be assumed to be at an incline which is at an angle of θ(kindly see both the pics in the pdf file). The value of θ will continuously change and so will the value of friction. I'm not able to figure out, why my solution is wrong, if it is wrong .
TL;DR Summary: I came across this question from a Sri Lankan A-level textbook. Question - An ice cube with a length of 10 cm is immersed in water at 0 °C. An observer observes the ice cube from the water, and it seems to be 7.75 cm long. If the refractive index of water is 4/3, find the height of the ice cube immersed in the water. I could not understand how the apparent height of the ice cube in the water depends on the height of the ice cube immersed in the water. Does anyone have an...
Back
Top