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PHY 241
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?
Vertically , v0=20cm/s `ds=0cm a=980cm/s
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What therefore are its final velocity, displacement, change in velocity and average velocity in the vertical direction?
`ds=120cm
vf^2 = v0^2 + 2 a `ds
vf^2 = 20^2 + 2 980cm/s^2 120cm
vf=485.4cm/s
`dv=485.4 cm/s
vAve=242.7 cm/s
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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?
Acceleration horizontally is 0 cm/s^2
`ds= vave *dt
120cm = 242.5cm/s dt
Dt=0.495s
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What therefore are its displacement, final velocity, average velocity and change in velocity in the horizontal direction during this interval?
Vf=80cm/s vAve=80cm/s `dv=0
`ds = vAve * `dt
`ds=80cm/s*0.495
`ds=39.6 cm
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After the instant of impact with the floor, can we expect that the ball will be uniformly accelerated?
Yes.
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There is no reason to expect the force experienced by the ball after first touches the floor to be uniform.
If it bounces then the acceleration will be uniform between bounces, but not during the intervals of contact with the floor that occur between the bounces.
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Why does this analysis stop at the instant of impact with the floor?
The motion and reaction of the ball and the floor will be erratic. We have no information on the properties of the floor. If the floor were wet dirt the ball would stop there. If it were hard tile the ball would bounce.
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