motion problem (please check)

A 8000N car is traveling 12 m/s along a horizntal road when the brakes are applied. The car skids to a stop in 4.0s. How much kinetic energy does the car have.

my work:

W= 8000N/9.18m/s
mass= 815.49 kg
Kinetic energy= (1/2mv^2-1/2mv^2)
kinetic energy=1/2 (815.49)(0)^2 - 1/2 (815.49)(12 m/s)^2 =5.0 X 10^4 J
Does this seem right

I think the issue is number of significant digits. Taking it to two, I get 5.8 If you use the 8000 as one sig digit, the answer is 6*10^4 J.

so I have the right idea

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asked by Jenny

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