What torque would have to be applied to a rod with a length of 4 m4m and a mass of 3 kg3kg to change its horizontal spin by a frequency of 3 Hz3Hz over 2 s2s?

1 Answer
Nov 18, 2016

The torque applied to the rod is 37.68 Newton-metre.

Explanation:

Torque is defined as the product of moment of inertia and angular acceleration
=>tau=Ialphaτ=Iα
Moment of inertia of rod is I_"rod"=((ML^2)/12)Irod=(ML212) and angular acceleration is change in angular velocity with respect to time
=>alpha=omega/tα=ωt
angular velocity omega=2pinuω=2πν as frequency is given in above case.
Now the torque becomes tau=[(ML^2)/12][(2pinu)/t]τ=[ML212][2πνt]
Substituting the given values we get,
tau=[[(3kg)(4m)^2]/12][(2xx3.14xx3Hz)/(2s)]τ=[(3kg)(4m)212][2×3.14×3Hz2s]
:.torque tau=37.68N-m.