course PHY 201
9/20 11:52 pm
At clock time t = 4 sec, a ball rolling straight down a hill is moving at 5 m/s and is 78 m from the top of the hill, while at clock time t = 9 sec it is moving at 7.5 m/s and is 114 m from the top of the hill. What is its average velocity during this time? What is its average acceleration during this time? Is it possible that the acceleration is uniform?
vAve = 6.25 m/s
aAve = 1/2 m/s^2
No, I don’t believe the acceleration is uniform. I think that it can’t be because the velocity isn’t uniform. The velocity isn’t uniform because when it is uniform, the final velocity is equal to twice the average velocity.
Good try, but When velocity is uniform AND initial velocity is zero, the final velocity is equal to twice the average velocity. The initial velocity isn't zero, though, so this argument doesn't apply here.
You don't say how you got the average velocity. You could have averaged initial and final velocities or you could have used the definition of average velocity. The two don't necessarily give you the same result. If they don't, the acceleration isn't uniform. If they do, then it is possible for acceleration to be uniform (though it isn't necessarily so).
What do you get if you average the init and final velocities on this interval?
What do you get from the definition of average velocity?
What therefore are your conclusions?