A solid disk with a radius of #1 m# and mass of #2 kg# is rotating on a frictionless surface. If #72 W# of power is used to increase the disk's rate of rotation, what torque is applied when the disk is rotating at #4 Hz#?

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Answer 1 · 2017-10-24T05:14:40

The torque is #=2.86Nm#

The mass of the disc is #m=2kg#

The radius of the disc is #r=1m#

The power #=P# and the torque #=tau# are related by the following equation

#P=tau omega#

where #omega=# the angular velocity

Here,

The power is #P=72W#

The frequency is #f=4Hz#

The angular velocity is #omega=2pif=2*pi*4=(8pi)rads^-1#

Therefore,

the torque is #tau=P/omega=72/(8pi)=2.86Nm#