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## Homework Statement

The mass of a minibus with the driver is 1.5*10^3 kg. The driver is moving at a speed of 30m.s when he notices that the traffic lights ahead have turned red. He applies a force of 9*10^3 N on the brake pedal.

A) How far must he have been from the traffic lights if he were able to stop in time?

## Homework Equations

a=Fnet/m

s=d/t

## The Attempt at a Solution

a=9*10^3/1.5*10^3

= 6 m.s^-2

using the equation a=v/t i got a time of 5 seconds

so

d = s*t

= 30*5

= 150 m but my textbook says it is 75 m