# Find the displacement in a word problem

**1. The problem statement, all variables and given/known data**

A car is slowing down at a rate of 20 km/h/s. How far does it travel if its original velocity is 50 km/h and its final velocity is 5.0 m/s?

**2. Relevant equations**

v_{f}^{2} = v_{0}^{2} + 2aΔx

**3. The attempt at a solution**

v_{f}^{2} = v_{0}^{2} + 2aΔx

Δx = (v_{f}^{2} – v_{0}^{2}) / 2a

= (18^{2}-50^{2}) / 2(-20)

= -2176 / -40

= 54.4 m

That’s wrong, though. The answer should be 15 m.

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