Posted by **Allison** on Friday, July 8, 2011 at 10:33am.

consider a cart being pulled up an inclined plane by a student during a Physics lab. The applied force on the cart is 18 N is directed parallel to the incline to cause the cart to be displaced parallel to the incline for a given displacement of 0.7 m. The initial energy plus the work done by the external force equals the final energy. If the cart begins with 0 Joules of energy, and the student does 12.6 Joules of work (F•d•cosine of angle = 18 N•0.7 m•cosine 0 degrees = 12.6 J), then the cart will finish with 12.6 Joules of mechanical energy. The final energy (12.6 J) is equal to the initial energy (0 J) plus the work done by external forces (12.6 J).

I am just wondering, how would the situation differ if there had been friction acting in the opposite direction on the cart?

would the mechanical energy possessed by the cart be less?