Jul 22, 2011
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Pre-Medical
A 2-kg cart starts on a 2m high table before it slides down a 30 degree ramp with coefficient of friction 0.20 and then comes to a complete rest 1.31m from the ramp on a horizontal surface. How much work was done to stop the car?

Its a discrete problem.

So, I got this question right using W = PEf - PEi, but I wanted to solve this problem using the other method, W = F x d.

To do so, I found the distance of the ramp first by using sin30 = 2/H (came out to be 4m).
Then, the total distance is 4 + 1.31 = 5.31m.

On the ramp, the work done by frictional force is umgxcos30xd, which is around 13.8.
On the ground, the work done by it is umgxd, which is around 5.24..

So, the total work done by it is around 19, which is not equal to 40 (the answer I got from PEf - PEi).

Can anyone help me find my mistake here?
 
OP
brood910
Jul 22, 2011
1,507
316
Status
Pre-Medical
OMG I FEEL SO STUPID NOW.
NVM ABOUT THIS.
They did not give us the coefficient of the ground.