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PHY 121
Your 'cq_1_13.1' report has been received. Scroll down through the document to see any comments I might have inserted, and my final comment at the end.
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A ball rolls off the end of an incline with a vertical velocity of 20 cm/s downward, and a
horizontal velocity of 80 cm/s. The ball falls freely to the floor 120 cm below.
For the interval between the end of the ramp and the floor, hat are the ball's initial
velocity, displacement and acceleration in the vertical direction?
v0=0m/sec
'ds=120cm=1.2m
a=9.8m/s^2
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What therefore are its final velocity, displacement, change in velocity and average velocity
in the vertical direction?
vf^2=v0^2+2a'ds
=2*9.8m/sec^2*1.2m
=23.52m/sec
=4.85m/sec
'dv= 4.85m/sec
vave = 2.425
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What are the ball's acceleration and initial velocity in the horizontal direction, and what
is the change in clock time, during this interval?
v0=0.8m/sec
a=0
'dt = sqrt(2'dsa)
=sqrt (23.52m/sec)
=4.85m/sec
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@& This isn't correct, and since you have the formula right I suspect a units error. My guess is that you had `ds in cm and a in m/s^2. You need to either express `ds in cm and a in cm/s^2, or alternatively express `ds in meters and a in m/s^2.
`dt won't come out in units of m/s.*@
What therefore are its displacement, final velocity, average velocity and change in velocity
in the horizontal direction during this interval?
'ds=(vo+vf)/2*'dt
=(0.8+0)/2*4.85
= 1.94meters
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After the instant of impact with the floor, can we expect that the ball will be uniformly
accelerated?
No because there is a resisting force that will change acceleration when it first hits the floor and each subsequent hit thereafter.
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Why does this analysis stop at the instant of impact with the floor?
The equations we use here are assuming uniform accelartion.
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*#&!
@& Your strategy on this problem was good. You had some errors in detail.
&#See any notes I might have inserted into your document, and before looking at the link below see if you can modify your solutions. If there are no notes, this does not mean that your solution is completely correct.
Then please compare your old and new solutions with the expanded discussion at the link
Solution
Self-critique your solutions, if this is necessary, according to the usual criteria. Insert any revisions, questions, etc. into a copy of this posted document. Mark any insertions with &&&& so they can be easily identified.If your solution is completely consistent with the given solution, you need do nothing further with this problem. &#
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