Non-conservative work energy theorem and potential energy

[blueblast]

Here is problem I quickly made up:

Suppose there is a ramp with a height of 6 meters and length of 12 meters. A block of 5 kg is pushed up to the top of the ramp with a constant velocity. The force of friction is 15 N.

Here's the confusion:

By using the non-conservative force work energy theorem, Work done by friction(Wf) = (KEf-KEi) + (PEf-PEi).

Since the block is pushed up at a constant velocity, the change in KE is zero. And since the block start from the ground, PEi is zero. So, Wf = PEf. Wf = friction * distance = 15 N * 12 meters = 180. So PEf = 180.

However, mgh says that potential energy is 5 kg * 6 meters * 9.8 m/s^2 =294.

Could someone please tell me where I am wrong? A diagram of the problem is attached just in case my words weren't clear.

 

[jbriggs444]

Since the block is pushed up

That sounds like a source of energy that you have not accounted for.

 

[nasu]

Friction is not the only force acting on the block. What makes the block to go up the ramp?

 

[blueblast]

That sounds like a source of energy that you have not accounted for.

Ah, I see my mistake now. Thanks!