posted by greg .
A ball initially moving at 0.5m/s rolls down a straight slope, accelerating at 0.25m/s^2 for 4 sec, how far does the ball travel in this time?
The speed at the end of the 4 seconds is
0.5 + 1.0 = 1.5 m/s
The average speed during the 4 second interval is (0.5 + 1.5)/2 = 1.0 m/s
Multiply that average by 4 s for the distance travelled.