A child's top is held in place, upright on a frictionless surface. The axle has a radius of r= 2.21 mm. Two strings are wrapped around the axle, and the top is set spinning by applying T= 2.40 N of constant tension to each string. If it takes 0.830 s for the string to unwind.

1- How much angular momentum does the top acquire? Assume that the strings do not slip as the tension is applied.

2- If the final tangential speed of point P, h= 35.0 mm above the ground, is 1.15 m/s and the angle theta is 26.0 what is the top's moment of inertia?

1 answer

1) torque = F * r
in this specific question
F = T = 2.40 N
r = diameter = 2 *.00221m
so
torque = 2.40 N * 2 * .00221 m = .010608
then
torque = L/t
t =0.830 s
0.010608 = L/0.830
L= 0.01278 or 1.28 x 10^(-2)