The rate of rotation of a solid disk with a radius of #8 m# and mass of #5 kg# constantly changes from #5 Hz# to #17 Hz#. If the change in rotational frequency occurs over #3 s#, what torque was applied to the disk?

1 Answer
Junaid Mirza
Nov 11, 2017

#"4021.2 Nm"# of torque was applied to disc.

Explanation:

Torque is rate of change of angular momentum.

#T = (I(omega_f - ω_i))/t#

#= (I2pi(f_f - f_i))/t#

#= ((mr^2)/2 2pi(f_f - f_i))/t# ………[∵ Moment of inertia of disc about is central axis is #(mr^2)/2#]

#= (("5 kg × (8 m)"^2)/2 × 2 π (17 - 5) "Hz")/"3 s" = "4021.2 Nm"#

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