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Yuki888 [10]
3 years ago
11

An object is dropped from a platform 400 ft high. Ignoring wind resistance, how long will it take to reach the ground?

Physics
1 answer:
irakobra [83]3 years ago
8 0
Let's convert the initial height from feet to meters first:
h=400 ft=121.9 m

The object is in free fall, so it is moving by uniformly accelerated motion with constant acceleration g=9.81 m/s^2 (gravitational acceleration) from initial height h=121.9 m. Its vertical position at time t is given by
y(t)=h- \frac{1}{2}gt^2

We want to know how long it will take to reach the ground, therefore we should calculate the time t at which the vertical position y(t) becomes zero:
0=h- \frac{1}{2}gt^2
rearranging,
t= \sqrt{ \frac{2h}{g} }= \sqrt{ \frac{2(121.9 m)}{9.81 m/s^2} }=4.98 s
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