Determine the Magnitude of the Time Rate of Change of Angular Momentum

[Northbysouth]

Homework Statement

In an experiment an individual throws a rock with an initial horizontal velocity of v₀ = 20 ft/s at time t=0. The rock is thrown from the edge of a cliff (directly above the base of the cliff) at height h=50 ft from the ground. The origin is assigned at the base of the cliff. Determine the magnitude of the time rate of change of the angular momentum of the rock about O (H'_O) at time t = 1 second

Homework Equations

H_O = rXmv

H'_O = M_O

The Attempt at a Solution

I think that r = 50 ft j

But how do I find the force from the given velocity?

Any help would be appreciated.

 

[haruspex]

What force?
Can you write down equations for the horizontal and vertical speeds at time t?