Question

Two motor-cyclists travel towards each other from points A and B. The motor-cyclist decelerates uphill from an initial velocity of 72 km/hr at point A with a deceleration of 2m/sec2 , the other accelerates downhill from an initial velocity of 36 km/hr at point B with an acceleration of 2m/se2. Find the time it takes for the motor-cyclists to meet and the distance travelled in this time by the first motor-cyclist, if the distance between points A and B is 300 m. Show how the distance between the two motor-cyclists changes with time. Plot the distance between the two motor-cyclists as a function of time. How may one determine from this diagram the moment when the two meet?

Answer 1

Answer: t = 10sec. l1 = 100m.

Explanation:

The distance between the motor-cyclists decreases uniformly with time in accordance with the formula l = * — t(v1 + v2), and drops to zero in 10 sec (Fig.).

If the meeting point is at a distance l1 from point A and l2 from point B, then