Physics

Problem

A train starts from rest and accelerates uniformly at

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

for

20\,\text{s}

. It then moves with the speed it has reached for the next

60\,\text{s}

. Calculate the total distance covered during the

80\,\text{s}

of motion.

Intuitive explanation

This problem breaks into two distinct phases: acceleration and constant velocity. The key is to find the final speed after the acceleration phase—that becomes the speed for the second phase. Then use the kinematic equation for uniform acceleration ( $s = ut + \frac{1}{2}at^2$ ) for phase one, and simple distance-equals-speed-times-time for phase two, before adding them together.

Intuitive explanation

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