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## anonymous one year ago PROJECTILE MOTION A cannon shoots horizontally off a 90 m high cliff with a speed of 90 m/s. How much time until the cannonball hits the ground?

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1. matt101

All you're interested in is stuff going on in the vertical direction. This means its horizontal speed doesn't affect your answer. So what do we know? Starting vertical speed, v0 = 0 m/s (cannonball starts from rest) Vertical acceleration, a = 9.8 m/s^2 (gravity) Vertical distance, d = 90 m (height of the cliff) We want to find time, t. What equation can we use to solve for t using the variables we already have?

2. anonymous

$$\color {maroon}{\text {This}~\text {is} ~ \text {what}~ \text {I've}~\text{done}\text{:}}$$$\Delta_y=V_yt+\frac{1}{2}at^2$$-90=-4.9t^2$$t=4.29 s$ @matt101

3. matt101

Looks good!

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