# Homework Help: Determine the Magnitude of the Time Rate of Change of Angular Momentum

1. May 13, 2013

### Northbysouth

1. The problem statement, all variables and given/known data
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

2. Relevant equations

HO = rXmv

H'O = MO

3. 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.

2. May 14, 2013

### haruspex

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

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