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course Phy 121
cq_1_131#$&*
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.
** CQ_1_13.1_labelMessages **
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 = 0 cm/s
'ds = 120 cm
a = 980 cm/s^2
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A downward velocity of 20 cm/s is in the vertical direction, so v0 isn't 0 for your vertical motion.
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&&&& v0 = 20 cm/s
'ds = 120 cm
a = 980 cm/s^2
What therefore are its final velocity, displacement, change in velocity and average velocity in the vertical direction?
vf^2 = v0^2 + 2 a `ds
vf^2 = 0 + 2 * 980 * 120
vf = 485 cm/s
'dv = 485 cm/s
vAve = (485 + 0) / 2 = 243 cm/s
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This solution is still based on v0 = 0. It needs to be modified for your corrected value of v0.
You also need to find the time required for the ball to fall.
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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 = 80 cm/s
vf = 20 cm/s
a = 980 cm/s^2
980 = 60 / 'dt
'dt = 0.06 s
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The 20 m/s is downward, so that quantity is vertical.
The 980 cm/s^2 acceleration of gravity is also vertical, not horizontal.
No forces act in the horizontal direction, so the horizontal acceleration is zero.
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&&&& a = 0 cm/s^
vf = v0 = 80 cm/s
What therefore are its displacement, final velocity, average velocity and change in velocity in the horizontal direction during this interval?
'ds = (50) * (0.06)
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The .06 s came from your assumption that the horizontal acceleration was 980 cm/s^2.
It's not clear where 50 came from or what it means.
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'ds = 3.06 cm
vAve = 50 cm/s
vf = 20 cm/s
'dv = 60 cm/s
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After the instant of impact with the floor, can we expect that the ball will be uniformly accelerated?
No
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Why does this analysis stop at the instant of impact with the floor?
There is no given data about how the ball travels after the fall.
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*#&!
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Your overall approach is good, but you need to clearly distinguish the quantities that apply to the vertical motion, and those that apply to the horizontal motion.
&#Please see my notes and submit a copy of this document with revisions, comments and/or questions, and mark your insertions with &&&& (please mark each insertion at the beginning and at the end).
Be sure to include the entire document, including my notes.
&#
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You have revised some of your quantities, but those quantities affect all of your results. You need to recognize and make all necessary corrections throughout the problem.
&#Please see my notes and submit a copy of this document with revisions, comments and/or questions, and mark your insertions with &&&& (please mark each insertion at the beginning and at the end).
Be sure to include the entire document, including my notes. &#
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