# physics plz?

A car is going 10 kph. The driver hits the brakes and the car travels 1 m after the brakes are applied. A while later the same car is going 20 kph. The driver hits the brakes. About how far does the car go after the brakes are applied?

### 1 Answer

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- FiremanLv 74 months ago
By work energy relation:

=>W = ΔKE

=>F x s1 = 1/2mu1^2

=>F = [(1/2mu1^2)/s1] ----------------(i) {this will remain constant}

2nd condition:Again by work energy relation:

=>W = ΔKE

=>F x s2 = (1/2mu2^2)

=>[(1/2mu1^2)/s1] x s2 = 1/2mu2^2

=>s2 = [(u2/u1)^2] x s1

=>s2 = [(2u1/u1)^2] x s1 {as u2 = 2u1}

=>s2 = 4 x s1

=>s2 = 4 x 1

=>s2 = 4 m

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