(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

A lorry is driving at 96 km h^−1. The driver decelerates to a speed of 48 km h^−1. Given that the deceleration is 2.68 m s^−2 find the distance over which the brakes are applied.

I know the initial speed of the lorry, v = 96 km h^-1 = 26.67 m s^-1

I know the final speed of the lorry, u = 48 km h^-1 = 13.33 m s^-1

I know the deceleration rate of the lorry, a = 2.68 m s^-2

so I'm looking for d (Distance)

2. Relevant equations

t=(v-u)/a to find the time t the breaks were applied for

d = vt + 1/2 x at^2 ?? to find the distance travelled while decelerating?

3. The attempt at a solution

Substitute the values for v,u and a to find speed s

t=(26.67 m s^-1 - 13.33 m s^-1)/2.68 m s^-2

= 4.98 s

I'm not sure what the second equation is for working out distance the lorry has travelled based on a decelerating body and the info I now have.

so I think d= (26.67 m s^-1 x 4.98 s) + 1/2 x 2.68 m s^-2 x 4.98 s^2?

Also, if this is correct and based on the information that I have, is there any other equation I could use to also find distance? I ask as the question's hint tells me to consider the energies involved and the section just read is also related to energy and force...

Many thanks

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# Homework Help: Finding the distance from deceleration

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