Determine the magnitude of the angular acceleration of the discus

[UrbanXrisis]

A discus thrower accelerates a discus from rest to a speed of 25 m/s by whirling it though 1.25 rev. Assume the discus moves on the arc of a circle 1m in radius.

Determine the magnitude of the angular acceleration of the discus:

ω=angular velocity

ω=v/r=25m/s / 1m = 25rad/s

ω^2=2ad
(25rad/s)^2=2a1.5(pi2)
a=33m/s^2

is this correct?

 

[xanthym]

A discus thrower accelerates a discus from rest to a speed of 25 m/s by whirling it though 1.25 rev. Assume the discus moves on the arc of a circle 1m in radius.

Determine the magnitude of the angular acceleration of the discus:

ω=angular velocity

ω=v/r=25m/s / 1m = 25rad/s

ω^2=2ad
(25rad/s)^2=2a1.5(pi2)
a=33m/s^2

is this correct?

{Total Distance Moved} = d = (1.25 rev)*(2*Pi*r) = (1.25 rev)*{2*Pi*(1 m)} = 7.854 m
{Acceleration} = (v^2)/(2*d) = {(25 m/sec)^2}/{2*(7.854 m)} = 39.79 m/sec^2
{Angular Acceleration} = {Acceleration}/r = {39.79 m/sec^2}/(1 m)
{Angular Acceleration} = 39.79 rad/sec^2


~~

 

[Doc Al]

ω=v/r=25m/s / 1m = 25rad/s

ω^2=2ad
(25rad/s)^2=2a1.5(pi2)
a=33m/s^2

is this correct?

Your method is correct but you plugged in 1.5 instead of 1.25. Correct that error and you'll get the answer that xanthym posted.