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A student drops an object out the window of the top floor of a high-rise dormitory.

ANeglecting air resistance, how fast is the object traveling when it strikes the ground at the end of 4.0 s? First used standard British units and then express the speed in mi/h for a familiar comparison.

How far, in meters, does the object fall during the 4.0 s? Comment on how many floors the dormitory probably has. (Assume that there are 32 floors/100 m.)

Verified Answer :

AL2006


-- The acceleration due to gravity is 32.2 ft/sec² .  That  means that the
speed of a falling object increases by an additional 32.2 ft/sec every second.

-- If dropped from "rest" (zero initial speed), then after falling for 4 seconds,
the object's speed is (4.0) x (32.2) = 128.8 ft/sec.

-- 128.8 ft/sec = 87.8 miles per hour

Now we can switch over to the metric system, where the acceleration
due to gravity is typically rounded to 9.8 meters/sec² .

-- Distance = (1/2) x (acceleration) x (time)²

       D = (1/2) (9.8) x (4)² =  78.4 meters

-- At 32 floors per 100 meters,  78.4 meters = dropped from the 25th floor.


The 5 points are certainly appreciated, but I do wish they were Celsius points.


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