Instructor: Dr. Bruce Law, CW
327, Tel: 532-1618.
E6. Yes, the automobile in this case would be slowing down, i.e. decelerating.
E8. (a) Yes, your velocity does change because your direction changes from north to east. (b) Yes, you are accelerating because your velocity is changing. Recall Acceleration = change in velocity/change in time.
E11. No, you don`t know if both cars accelerated over the same or different periods of time.
(Recall that acceleration = change in velocity/time.)
E14. (a) Yes, if an object is moving at constant velocity then its acceleration is zero. (b) Yes, eg. if you throw a ball in the air, at the top of its flight, its speed is zero while its acceleration due to gravity is still 10m/s/s, down.
P2. Acceleration = (final velocity - initial velocity)/time = (0 - 100 km/h)/10 s = -10 km/h/s
P3. Since it starts going up at 30m/s and loses 10m/s each second, its time going up is 3 seconds. Its time returning is also 3 seconds, so it`s in the air for a total of 6 seconds. Distance up (or down) is 0.5gt2 = 5 x 32 = 45m.
P5. Instantaneous velocity v = gt = 10m/s/s x 10s = 100m/s, down.
Average velocity = (vi + vf)/2 = (0 + 100)/2 = 50m/s, down.
Distance, d = 0.5gt2 = 0.5 x 10 x 102 = 500m