2 ways to solve a problem

There are sometimes different ways to arrive at an answer.
Consider a 1000Kg car sliding to a stop from an initial velocity of 10m/s with m=.2.
How much work is done by the frictional forces stopping the car?

USING ENERGY APPROACH	USING PREVIOUS METHODS
The car has kinetic energy. Once it has stopped, it has none. The energy lost is the kinetic energy, which equals the work done... KE = mv²/2 = 1000Kg(10m/s)²/2 = 50000J*	First find the acceleration of the car = a = F/m = mN/m = .21000Kg9.8m/s/s / 1000Kg = .29.8m/s/s = 1.96m/s/s*
	Next, we know Vf=0m/s and Vo=10m/s and a=1.96m/s/s, so we solve for "x" using a kinematic equation... x = (Vf² - Vo²)/2a = (-10m/s)²/(21.96m/s/s) = 25.51m*
	Next, we know the force acting and we know the distance so we can solve for work... W = fx = mNx = (.21000Kg9.8m/s/s)25.51m = 50000J*

What do I hope you have learned from this page?

There is often no single "right way" to do a problem.

You can get the right answer if you follow a logical process.

Sit and look at the problem for a moment to see if there is an approach you think you should follow. Will other ways work too? Pick a route and follow it.