#$&* course Phy 201 4:39 pm EST 6/14/14 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 = 'ds/'dt = (114-78)/(9-5s) = 36/5 = 7.2 m/s aAve = 'dv/'dt = 2.5m/a / 5s = 0.5 m/s^2. It the interval 4 to 9, acceleration could be uniform, because if you increase 0.5m/s/s for each second 4 through 5, you have 7.5m/s at second 9. However, at second 0, if you start out a 0 velocity, it would seem that at second 4, you would only be going at 2m/s. So from second 1-4, you would have to have a greater intial velocity than 0 or not have uniform velocity throughout this time, although velocity is uniform from 4 to 9 seconds.