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# Angular Momentum and Torque

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In the figure (please see the attachment), a 0.420 kg ball is shot directly upward at initial speed 37.5 m/s. What is its angular momentum about P, 2.20 m horizontally from the launch point, when the ball is at the following heights?

i) at max height, ii) when it is halfway to the ground.

Also find the torque on the ball about P at max height and halfway to ground.

© BrainMass Inc. brainmass.com October 2, 2022, 5:16 am ad1c9bdddf
https://brainmass.com/physics/angular-momentum/angular-momentum-torque-256844

## SOLUTION This solution is FREE courtesy of BrainMass!

Angular momentum of a particle about a point is defined as the moment of the linear momentum vector about the given point i.e. :

Magnitude of angular momentum = Magnitude of the linear momentum vector x Perpendicular distance of the line of action of the linear momentum vector from the given point

Perpendicular distance of the linear momentum vector from the given point = 2.2 m

a) Velocity of the ball at the highest point = 0

Linear momentum at the highest point = 0

Angular momentum at the highest point = 0

b) Initial kinetic energy of the ball = ½ mv2

At the highest point the ball will have only potential energy, Hence, mgh = ½ mv2

Or h = v2/2g = 37.52/2x9.8 = 71.75 m
_______
After falling through ½ the height (i.e. 35.9 m), its velocity will be v' = √2g(35.9) =
__________ ______
√2x9.8x(35.9) = √703.64 = 26.5 m/s

Linear momentum of the ball at ½ the height = mv = 0.42 x 26.5 = 11.13 kg.m/s

Magnitude of angular momentum = 11.13 x 2.2 = 24.5 kg.m2/s.

As the ball moves clockwise with respect to the given point, the direction of the angular momentum vector is into the x-y plane i.e. towards -z axis.

c) At any point between the lowest and the highest point, the ball is subjected to a force equal to its weight i.e. 0.42 x 9.8 = 4.1 N

Torque is defined as the moment of the force vector about the given point i.e. :

Torque = Magnitude of the force vector x Perpendicular distance of the line of action of the force vector from the given point

Hence, torque at all points between the lowest and the highest points = 4.1 x 2.2 = 9 Nm (towards -z axis).

This content was COPIED from BrainMass.com - View the original, and get the already-completed solution here!

© BrainMass Inc. brainmass.com October 2, 2022, 5:16 am ad1c9bdddf>
https://brainmass.com/physics/angular-momentum/angular-momentum-torque-256844