#$&*
PHY 121
Your 'cq_1_22.2' report has been received. Scroll down through the document to see any comments I might have inserted, and my final comment at the end.
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cq_1_222
#$&*
PHY 121
Your 'cq_1_22.2' report has been received. Scroll down through the document to see any
comments I might have inserted, and my final comment at the end.
** **
A 70 gram ball rolls off the edge of a table and falls freely to the floor 122 cm below.
While in free fall it moves 40 cm in the horizontal direction. At the instant it leaves
the edge it is moving only in the horizontal direction. In the vertical direction, at this
instant it is moving neither up nor down so its vertical velocity is zero. For the
interval of free fall:
What are its final velocity in the vertical direction and its average velocity in the
horizontal direction?
answer/question/discussion: ->->->->->->->->->->->-> : ->->->->->->->->->->->-> :
122cm = 0.122 m
vf = sqrt(2*9.8m/sec^2*0.122m)
vf = 1.55m/sec
@& Good, but note that 122 cm is 1.22 m, not .122 m.
It's OK though. We can analyze this for a 12.2 cm drop.*@
vave = (1.55/2) = 0.775m/sec Which seems very wrong.
@& This part is wrong. The 1.55 m/s would be the final velocity in the vertical direction,
and would not apply to the horizontal direction.
However .775 m/s is useful, being the average vertical velocity of the falling ball. Use it
to find the time of fall. (remember that you're calculating for a 12.2 cm = .122 meter
drop, not the 122 cm = 1.22 m drop of the original question).
Then use your time interval and the given information to anwer the question about the
horizontal velocity.*@
### 'dt = 'ds/vAve
'dt = 0.122m/0.775m/sec
'dt = 0.157 sec
'ds = 0.122m
'dt = 0.157 sec
Still not sure how to get horizontal velocity. It seems that the above information is all
we know about horizontal movement?
vAve = 'ds/'dt
vave = 0.77m/sec
@& This is vAve in the vertical direction.
The question is now asking about motion in the horizontal direction.
You have analyzed the vertical motion correctly and you have the time of fall, which is `dt = .156 sec, which is now correct.
The ball moves 40 cm in the horizontal direction as it falls. What therefore is its horizontal velocity?*@
Same thing as above which I know is wrong.
#$&*
Assuming zero acceleration in the horizontal direction, what are the vertical and
horizontal components of its velocity the instant before striking the floor?
answer/question/discussion: ->->->->->->->->->->->-> : ->->->->->->->->->->->-> :
I know it will be the horizontal and vertical velocity but I do not know how to get there
from here.
#$&*
What are its speed and direction of motion at this instant?
answer/question/discussion: ->->->->->->->->->->->-> : ->->->->->->->->->->->-> :
Same as above.
#$&*
What is its kinetic energy at this instant?
answer/question/discussion: ->->->->->->->->->->->-> : ->->->->->->->->->->->-> :
And again, not sure how to get to this point.
#$&*
What was its kinetic energy as it left the tabletop?
answer/question/discussion: ->->->->->->->->->->->-> : ->->->->->->->->->->->-> :
#$&*
What is the change in its gravitational potential energy from the tabletop to the floor?
answer/question/discussion: ->->->->->->->->->->->-> : ->->->->->->->->->->->-> :
#$&*
How are the the initial KE, the final KE and the change in PE related?
answer/question/discussion: ->->->->->->->->->->->-> : ->->->->->->->->->->->-> :
#$&*
How much of the final KE is in the horizontal direction and how much in the vertical?
answer/question/discussion: ->->->->->->->->->->->-> : ->->->->->->->->->->->-> :
#$&*
*#&!*#&!
@& See my note in response to your new work and see if you can take this a step further.
&#Please see my notes and, unless my notes indicate that revision is optional, submit a copy of this document with revisions 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.
If my notes indicate that revision is optional, use your own judgement as to whether a revision will benefit you. &#
*@