Physics equations of motion Question

a) Two stopping places for a train are 12km apart and the journey between them takes 20 minutes. If the train accelerates uniformly for three quarters of the distance and then decelerates uniformly to rest for the last quarter, calculate the maximum speed of the train in metres per second.
b) A sprinter can attain a maximum speed of 10 m/s and can maintain this to the end of a 100m race. If his time for the race is 11.0s, what is his acceleration

Reply 1

Joinedup

I'd start with a sketch of a speed time graph.

for the first section the graph is going to be a triangle with a base (b) equal to the journey time and the area under the triangle (a) is the distance covered. The peak (h) of the triangle is going to be the top speed.

for a triangle a = bh/2

best to convert distance to meters and time to seconds before starting IMO