# Homework Help: Calculation of work

1. Nov 18, 2007

### Jacque77

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

The (non-conservative) force propelling a 1.10 x 10(3)-kg car up a mountain road does 6.80 x 10(6) J of work on the car. The car starts from rest at sea level and has a speed of 22.0 m/s at an altitude of 1.90 x 10(2) m above sea level. Obtain the work done on the car by the combined forces of friction and air resistance, both of which are non-conservative forces.
Calculate the work done by non-conservative forces using Wnc = dKE +DPE where
Wnc= W friction+W air+W engine

2. Relevant equations
I used W1= .5MV2 + MGH
and
required W =W1-W

3. The attempt at a solution

.5*1100kg*(22squared m/s) + 1100kg*9.8*192m = 2335960J

2335960-6800000 = -1655960J
What did I do wrong?

2. Nov 18, 2007

### rl.bhat

Work done on the car - work done by the car = loss of energy due to friction, air resistance.

3. Nov 18, 2007

### Jacque77

the 2335960-6800000 gives -4464040 which is the correct answer. Too tired to see how unreasonable the first result was!!!