course Phy 121
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.687, .234
.921, .281
.812, .281
.567, .359
From these times I determined the average velocities at which the ball traveled for each portion of the run:
14.8cm/s, 67.4 cm/s
16.8cm/s, 55.2 cm/s
19.1cm/s, 55.2 cm/s
27.3cm/s, 43.2 cm/s
The average velocity of the ball on the lower half of the ramp is approximately three times that of the ball on the initial half.
060406_questions
What do we mean by velocity?
The class notes define velocity as the time required to move an object through a known displacement.
How can we determine the velocity of a ball rolling down an incline?
We measure the incline and time the ball as is completes the run on the ramp. We divide the distance by the time to determine the velocity.
We anticipate from our experience that a ball traveling down a greater incline, starting from rest, will experience a greater change in velocity. How can we determine whether the velocity actually changes, and whether the velocity increases in the manner that we expect?
If we time the ball as it travels down measured portions of the ramp, divide the distance traveled by the time it took, we can get the average velocity of each section of the run and compare the data.
How could we determine the velocity of the ball at a specific point?
If we set up a graph of velocity vs. clock time, we can measure the slopes at various distances using the specific point in time as a fixed point. As the slopes approach the slope of the tangent line, we can determine the acceleration at
that particular instant.
How do we determine the rate at which the velocity changes?
The rate at which velocity changes, or the acceleration, can be determined by dividing the change in velocity by the change in time.
How can we understand the concept of the rate at which velocity changes?
The easiest way to understand the concept of acceleration is to illustrate on a graph the changes in velocity on the y axis and the change in time on the x. It is immediately evident if the rate at which velocity changes is constant, increasing, or decreasing.
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Excellent work. Let me know if you have questions.