We will give solution to the following problem:

"A driver traveling at 70 km/h tries to stop the car and finds that the brakes have failed. The emergency brake is then pulled and the car comes to a stop in 120 m. Find the car’s deceleration."

u = 70 km/hr is the initial velocity 

v = 0 km/hr is the final velocity

s = 120 m = 120/1000 km = 0.12 km the distance covered

a = deceleration

We know that v^2 = u^2 + 2as and we plug the given values:

70^2 + 2*a*0.12 = 0^2

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click here to see the equation solved for a

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a = -20,416.67 km/hr^2

a = -20,416.67*1000/(60*60)^2 m/s^2

a = -1.58 m/s^2 approximately

The car's deceleration was 1.58 m/s^2.