- #1
Misr
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What is the work done in this case??
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.
F=ma
Vt-V0=at
W = F*d*cos theta
d = V0t+1/2 a t^2
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
Homework Statement
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.
Homework Equations
F=ma
Vt-V0=at
W = F*d*cos theta
d = V0t+1/2 a t^2
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