Magnitude of angular acceleration- my first post ever in physics forum

Join the discussion
Registration is free. Start your own thread to ask a follow-up.
Sign up Log in
8 replies · 2K views
sweetwilliam
Messages
12
Reaction score
0

Homework Statement



CD is playing for 74 min, starts at angular speed of 480 rpm then slows to 210rpm. what's the magnitude of the angular acceleration

Homework Equations


angular acceleration =ω/ t


The Attempt at a Solution


i converted the rev to rad then min to sec then divided by sec and got 50.3 rad/s and 14.7 rad/s ... 14.7-50.3=-35.6/4440s= -.0080 my book says its wrong...fyi this is my first pot in physics forum so i hope i did it all correct
 
Physics news on Phys.org

Discussion

Hi sweetwilliam , welcome to Physics Forums.

Your initial angular velocity value looks okay at 50.3 rad/s. You might want to check your value for the final angular velocity.
 
Hi, thanks...i re-did the final rev/min and got 29.43 but when i put that back into my formula I am still not getting the answer that's in the book...thanks
 
sweetwilliam said:
Hi, thanks...i re-did the final rev/min and got 29.43 but when i put that back into my formula I am still not getting the answer that's in the book...thanks

That value, 29.43, still doesn't look quite right. Can you expand on your calculation?
 
i took 281rev/min and multiplied it by 2pi then divided by 60 sec...thanks
 
oh sorry i meant 210 rev.min x 2pi then divide by 60 which =21.99
 
ok after using that number i got -.0064 rad/s^2 which is partially correct by why in the book does it say .0064, where did the neg. go?
 
sweetwilliam said:
ok after using that number i got -.0064 rad/s^2 which is partially correct by why in the book does it say .0064, where did the neg. go?

They asked for the magnitude of the acceleration. Magnitudes are always positive.