A train must travel between two stations

PHYSICS · Single correct · A Level · Physics · Mechanics and materials · Mechanics and materials

Problem

A train must travel

1.2\,\text{km}

between two stations. It starts from rest, accelerates uniformly at

1\,\text{m}\,\text{s}^{-2}

until it reaches

20\,\text{m}\,\text{s}^{-1}

, runs at this speed for some time, and finally decelerates uniformly at

2\,\text{m}\,\text{s}^{-2}

to come to rest at the next station. The minimum possible time for the journey is closest to (a)

70\,\text{s}

(b)

60\,\text{s}

(c)

75\,\text{s}

(d)

85\,\text{s}