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A rock is dropped from a 200 m high cliff. How long does it take to fall (a) the first 100 m and (b) the last 50 m?
The basic equation you want is:
s=at22
Solving for t:
t=2sa−−−√
We’ll assume a=9.8 , so 2a−−√=14.9−−−√≈0.4518
So, for (a)s=100 , so t=0.4518100−−−√=4.518
The total time is 0.4518200−−−√≈6.389
The time to fall 150 m is 0.4518150−−−√≈5.533
So the time to fall the last 50 m is 6.389 - 5.533 = 0.856 seconds
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Power is calculated as work per unit time, and work in turn is calculated as force multiplied by distance. In this case, the force required is equivalent to the weight of the barbell multiplied by acceleration due to gravity.
P = W/t = Fd/t = mgd/t = (200 kg)(9.81 m/s^2)(2 m)/2.2 s = 1783.64 Watts.
The x component of the force is 8.4N * cos(31°) = 7.2N (2 s.f.)
Explanation:
Below is an attachment containing the solution.
