Calculate the height of a bldg. by dropping a ball off the roof and timing it. Instead the student gave the stop watch to the janitor and asked him the height of the building (flunked assignment).
If it did take the ball say, 5 seconds to hit the ground, then the height of the building is 9.8 +19.6 +39.2+ 78.4 + 156.8 = 303 ft?
2006-06-21 17:29:22 · 5 answers · asked by Anonymous in Science & Mathematics ➔ Physics
a little unclear but ...
the 'usual' equation is :
s=1/2 * a * t^2
= .5 * 9.8 * 5^2
= 4.9 * 25
= 122.5 meters
oops .. in feet
s=.5 * 32 * 5^2 = 16 * 25 = 400 feet (which "should" equal 122.5 meters)
2006-06-21 17:37:29 · answer #1 · answered by atheistforthebirthofjesus 6 · 0⤊ 0⤋
actually, this is a calculus problem unless you use the equations for which the calculus has already been done for you
the general equation reduces to x=1/2 at^2 in this case
a is 9.8 meters/sec&2 or (32.2 ft/sec^2 if you want the answer in feet)
t is the time , in this case 5 seconds
the building height, x, equals .5*32.2*5^2
402.5 ft (of course, this assumes no air resistance so in a real case, the air would slow the ball down and the building would actually be shorter than this calcualtion predicts)
we usually ignore air resistance in these calculations because it helps us learn the principles in a simplified situation
2006-06-22 00:46:01 · answer #2 · answered by enginerd 6 · 0⤊ 0⤋
I don't see how that would be an accurate way to measure. We know that objects falling will accelerate at a steady pace. But, I would think you will need to know the final speed when it impacts in order to calculate height. (I could be wrong). Time is only one variable in the equation, and you need two to calculate.
Of course, there are other factors to consider, too. What about updrafts? An updraft would slow the object down, throwing off the calculations. The theory is based on an object being inside a vacuum. Of course our atmosphere is not a vacuum.
If they were trying to get a best guess, you would have to do it several times and average your results.
2006-06-22 00:42:59 · answer #3 · answered by jeffrey_meyer2000 2 · 0⤊ 0⤋
D=9.8 (t)
D=9.8 (5)
D= use ur calculator
9.8 is the speed that objects fall on earth(in a vaccum). (meters)
t is the time it takes for the ball to fall. (seconds)
this is all in meters.
2006-06-22 00:39:39 · answer #4 · answered by Anonymous · 0⤊ 0⤋
why are you doubling the distance travelled? I think you should just add 9.8 for each second.
or better yet, use the formula D = 9.8 * t^2/2, like atheist does below
2006-06-22 00:32:10 · answer #5 · answered by Anonymous · 0⤊ 0⤋