Question

A constant torque of 20Nm produces 5 rotations on a body of mass 10 kg. The work done on the body is: /

Answer 1

L₁ = initial angular momentum = 100 kgm²/s

L₂ = final angular momentum = ?

t = time interval during  which the torque acts = 7 - 4 = 3 sec

τ = torque applied on wheel  = 20 N-m

according to impulse -change in angular momentum equation

Torque x time interval = change in angular momentum

Using the equation

τ t = (L₂ - L₁)

inserting the values in the above equation

(20) (3) = (L₂ - 100)

60 = L₂ - 100

L₂ = 60 + 100

L₂ = 160 kgm²/s