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.
** **
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, what is the ball's initial velocity, displacement and acceleration in the vertical direction?
• What therefore are its final velocity, displacement, change in velocity and average velocity in the vertical direction?
• What are the ball's acceleration and initial velocity in the horizontal direction, and what is the change in clock time, during this interval?
• What therefore are its displacement, final velocity, average velocity and change in velocity in the horizontal direction during this interval?
• After the instant of impact with the floor, can we expect that the ball will be uniformly accelerated?
• Why does this analysis stop at the instant of impact with the floor?
1) v0=0cm/s, ‘ds=120cm, a=980cm/s^2. 2) vf^2=0cm/s^2+2(980cm/s^2)*120cm. vf=485cm/s. ‘ds=120cm. ‘dv=485cm/s. vAve=242.5cm/s. ‘dt=120cm/242.5cm/s=.49seconds. 3)v0=80cm/s. ‘dt=.49sec
good so far; you have the time of fall
a=(‘dv/’dt) a=(80cm/s/.49s) a=163cm/s^2.
this would be correct if the ball accelerated at a constant rate from rest to 80 cm/s; but that isn't the case here
4)’ds=40cm/s*.49sec=19.6cm. vf=0cm/s vAve=40cm/s ‘dv=80cm/s 5) No, gravity will then be decelerating the ball at a consistent rate. 6) Gravity will now be slowing the ball down the instant after impact, and we lose energy from several different means when the ball comes in contact with the ground which changes the scenario greatly.
** **
30minutes
** **
I did not feel to confident with this problem, mainly with the 5th and 6th question asked.
You did pretty well. See the link below to clarify the last part.
&#Please compare your solutions with the expanded discussion at the link
Solution
Self-critique your solutions, if this is necessary, according to the usual criteria. Insert any revisions, questions, etc. into a copy of this posted document. Mark any insertions with &&&& so they can be easily identified. &#