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.
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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:
Accel of gravity: 980 cm/s/s
vf^2 = v0^2 + 2 a `ds
vF^2 = 2(980)(122)
vF = 489 cm/s
vAve = 244.5 cm/s
122 = 244.5*'dt
'dt = .50 seconds
40 = vAve * .5
vAve = 80 cm/s
VF in vertical: 489 cm/s
vAve in horizontal: 80 cm/s
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:
x component = 80
y component = -489
What are its speed and direction of motion at this instant?
answer/question/discussion:
c = 495.5 cm/s
tan^-1(-489/80) = -80.7 degrees
So you could say the object is traveling at 495.5 cm/s 279.3 degrees counterclockwise from the x axis the instant before it hits the floor.
What is its kinetic energy at this instant?
answer/question/discussion:
KE = .5mv^2
KE = .5(.07)(4.955)^2
KE = .86 Joules
What was its kinetic energy as it left the tabletop?
answer/question/discussion:
kE = .5(.07)(.8)^2
KE = .02 Joules
What is the change in its gravitational potential energy from the tabletop to the floor?
answer/question/discussion:
Change would be .84 Joules
How are the the initial KE, the final KE and the change in PE related?
answer/question/discussion:
KEfinal - KE initial = Change in PE
How much of the final KE is in the horizontal direction and how much in the vertical?
answer/question/discussion:
The vector would be .86 Joules and the degrees would be -80.7
cos(279.3) = x/.86
x = .14
.86sin(279.3) = -.85
I thought it shouldve added up to .86.... I would guess though that since the ball didn't accelerate in the horizontal direction that its KE stayed the same
in the horizontal.. it only increased in the vertical
Horiz KE = .02 Joules
Vertical KE = .84 Joules
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30 min
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Very good work.