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phy 201
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.
** CQ_1_22.2_labelMessages **
Seed 21 q2
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: ->->->->->->->->->->->-> :
m=.07 kg
Ds=1.22 m
A=9.8 m/s
V0vert=0
Vf^2=2(9.8)(1.22)
Sqrt23.9
Vf=4.88 m/s vertical direction
Dv=4.88
A=dv/dt
Dv/a=dt
4.88/9.8=.5sec
Dt=.5 sec
vAve=ds/dt
1.22 m/.5s=
vAve=2.44 m/s
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Good.
Note that all these quantities apply to the vertical motion.
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• 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: ->->->->->->->->->->->-> :
y= -4.88
x= 2.44
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You have the correct vertical velocity.
However 2.44 m/s is the average vertical velocity, and is not related to the horizontal velocity.
You haven't yet figured out the horizontal motion.
You are given the horizontal displacement, which is 40 cm. You know that the horizontal acceleration is zero. You have figured out the time of fall.
So you need to complete your analysis of the horizontal motion.
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• What are its speed and direction of motion at this instant?
answer/question/discussion: ->->->->->->->->->->->-> :
not sure how to cacluate speed.
-63 maybe Im not really sure if my components are even correct
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Your vertical and horizontal velocities will be the x and y components of the velocity vector.
Speed is the magnitude of the velocity.
How do you find the magnitude and direction of a vector when you know its components?
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• What is its kinetic energy at this instant?
answer/question/discussion: ->->->->->->->->->->->-> :
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• What was its kinetic energy as it left the tabletop?
answer/question/discussion: ->->->->->->->->->->->-> :
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• What is the change in its gravitational potential energy from the tabletop to the floor?
answer/question/discussion: ->->->->->->->->->->->-> :
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• How are the the initial KE, the final KE and the change in PE related?
answer/question/discussion: ->->->->->->->->->->->-> :
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• How much of the final KE is in the horizontal direction and how much in the vertical?
answer/question/discussion: ->->->->->->->->->->->-> :
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25 min
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self-critique #$&*
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Solution
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Good start with the vertical motion.
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