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course Phy 231
2-19-11 about 12:00 pm
An object is given an unknown initial velocity up a long ramp on which its acceleration is known to have magnitude 5 cm/s^2. .325 seconds later it passes a point 5.6 cm up the ramp from its initial position. •What are its possible initial velocities, and what is a possible scenario for each?
What is the maximum distance the object travels up the ramp?
ds= 5.6cm
dt= .325s
a= -5cm/s^2 chosen to be negative since it goes up the ramp
vf= 0 assuming that it rolls to a stop
vAve= 5.6cm/.325s= 17.23cm/s
v0= 17.23cm/s * 2 - 0= 34.46cm/s
v0 could be -34.46cm/s if the ball is rolling down the ramp
Max distance is 29.7cm up the ramp
@& You can't assume that the ball comes to a stop after .325 seconds.
That would lead to the conclusion that the acceleration is 34 cm/s / (.325 sec) = 100 cm/s^2, which contradicts the given information.
You are given the three quantities `ds, `dt and a. These three quantities determine all the others, so you can't assume a value for a fourth quantity.
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