Phy 231
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A ball falls freely from rest at a height of 2 meters. Observations indicate that the ball reaches the ground in .64 seconds.
• Based on this information what is its acceleration?
answer/question/discussion: ->->->->->->->->->->->-> :
initial velocity = 0m/s
ds = 2m
dt = .64sec
vAve = 2m/.64sec = 3.125m/s
final velocity = 2*vAve = 2*3.125m/s = 6.25m/s
dv = 6.25m/s-0m/s = 6.25m/s
acceleration = 6.25m/s / .64s = 9.77m/s^2
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• Is this consistent with an observation which concludes that a ball dropped from a height of 5 meters reaches the ground in 1.05 seconds?
answer/question/discussion: ->->->->->->->->->->->-> :
5m = 0m/s(1.05s)+.5(9.77m/s^2)(dt^2)
5m = 4.885m/s^2 (dt^2)
Dt^2 = 1.02s^2
Dt = 1.01 seconds
No, the acceleration would have to be slower for the object to cover 5m in 1.05 seconds. The actual time is .04 seconds faster than the concluded interval.
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• Are these observations consistent with the accepted value of the acceleration of gravity, which is 9.8 m / s^2?
answer/question/discussion: ->->->->->->->->->->->-> :
In the first situation, the acceleration of the object is right at the acceleration due to gravity. In the second situation, if the acceleration were due to gravity, then the time would have been slower.
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20 minutes
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