Thursday, September 16, 2010

a ball is dropped from a height of 50 meters how far has it fallen after 2 seconds

We are asked to find the distance a ball has fallen in two seconds after it has been dropped from a height of 50 meters.


We assume that we can ignore all forces except gravity (e.g. we ignore wind resistance, etc...) We use the falling object model:


On Earth, the height of an object falling due to the force of gravity is given by where v nought is the initial velocity and h nought is the initial height above the ground (time in seconds and distance in meters.) Here v nought is zero (the ball is dropped, not thrown) and h nought is 50m. Thus:



However, the question was not to find the height at time t=2 seconds, but how far the ball had dropped. Since the initial height was 50m and the height at time t=2 is 30.4m, the distance dropped is 19.6m.

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