Angular momentum

Question

The motion of a 25kg mass on the end of a string is uniform circular motion. The magnitude of the tangential velocity of the mass is 5 m/s. The circular path is horizontal and the magnitude of the centripetal force is 4000 newton. Calculate the angular momentum of the mass.

Answer 1

The angular momentum for a mass, m, located at a distance, r, moving with tangential speed, v, from the origin is given by L = mvr. 

 

We know the mass and tangential speed but not r.

 

 

We can get the radius, r, by using the centripetal force: F_c = mv²/r or r = mv²/F_c.

 

 

Using this expression for r, L = mv(mv²/F_c) = m²v³/F_c

 

 

L = (25²)(5³)/4000 = 19.5 kg·m²/s