(adsbygoogle = window.adsbygoogle || []).push({}); What is the work done in this case??

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

A car of mass 1000 Kg moves with velocity 2 m/s , the brakes are applied to stop the car after 2 sec . Calculate the work done by the brakes.

2. Relevant equations

F=ma

Vt-V0=at

W = F*d*cos theta

d = V0t+1/2 a t^2

3. The attempt at a solution

F=ma

Vt-V0=at

0-2=2a

Then a = -1 m/s^2

k..

F = -1000 N

d = V0t+1/2 a t^2

d = 4 + (0.5*-1*4)=2m

since the force applied by the brakes is opposite to the displacement

then theta = 180 degrees

W = F*d*cos theta

W= -1000*2*-1 = 2000 joule

I'm sure that there's something wrong with my answer (to be more exact I think I've somethi wrong with the signs)

So could you help?

Thanks

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# Homework Help: What is the work done in this case?

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