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Physics- falling objects, parabola shape

Hey! I know that the horizonal and horizontal motion are unrelated, and the velocity remains the same (if there is no air resistance, friction etc)- this correlates with the whole 'shooting a gun and dropping a bullet at the same time, which one will hit the ground first? They will fall at the same time.' However, I don't know how to find the different parts of a problem.

For example:

A stone is thrown horizontally at a speed of 10 m/s from the top of the cliff 78.4 cm high. How long does it take the stone to reach the bottom of the cliff? How far from the base of the cliff does the stone strike the ground?

How also, if needed, would I find how fast a ball is going if it ended up going X far off a cliff X high? Or, how would I find how high the cliff is if I have the other two pieces of data?

Thanks!

:frown:
 
Last edited:

Chi Meson

Science Advisor
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Originally posted by havechanged


A stone is thrown horizontally at a speed of 10 m/s from the top of the cliff 78.4 cm high. How long does it take the stone to reach the bottom of the cliff? How far from the base of the cliff does the stone strike the ground
I assume you meant to say that you know that "vertical" and horizontal motion are independant.

The amount of time the stone remains in the air depends entirely on the vertical motion. It would take the same amount of time to hit the ground as if it were dropped. SO, can you calculate how long it would take a stone to drop straight down? THis the amount of time your stone is in the air, and so it is also the amount of time it is moving at 10 m/s in the horizontal direction. Now you have v and t. FInd d.
 

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