M1 exam question

A car starts from rest at a point S on a straight racetrack. The car moves with constant acceleration for 20s, reaching a speed of 25ms^-1. The car then travels at a constant speed of 25ms^-1 for 120s. Finally it moves with constant deceleration, coming to rest at a point F.

parts a) and b) are fine.

A motorcycle starts at S, 10s after the car has left S. The motorcycle moves with constant acceleration from rest and passes the car at a point P which is 1.5km from S. When the motorcycle passes the car, the motorcycle is still accelerating and the car is moving at a constant speed. Calculate.

c) the time the motorcycle takes to travel from S to P. (5)
d) the speed of the motorcycle at P. (2)

dist. travelled by car whilst accelerating = 1/2 x 20 x 25 = 250m
--> travelled 1250m whilst travelling at 25ms^-1
i.e. 25 x t = 1250; t = 50s
20 + 50 = 70s since car left S
--> 60s since bike left S
for bike:
s = (v+u)t/2
v = 2s/t - u
= 3000/60 - 0 = 50ms^-1

i get 50seconds and 50m/s too.

this is the nov 2003 paper rite? ive got 70 and 50. check on ajimal.com
he's got the same aswell

Answers are 60 seconds and 50ms^-1.