# physics

A motorist increase speed from rest and in 21s reaches am a speed of 20km/hr.What is (a)the uniform acceleration in ms-2?(b)the distance covered in the time interval?

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1. Just dust off your good old formulas:

v = at
s = 1/2 at^2

First, get better units:

20 km/hr * 1000m/km * hr/3600sec = 5.555m/s

Velocity changed from 0 to 5.555m/s in 21s.

v = at
5.555 = 21a
a = 0.265m/s^2

s = .5at^2 = .5*0.265*21^2 = 58.43m

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