**(New tips are continually
added to these pages. Check back in a few months' time for more)**

**TOPIC 4:
Work, Energy and Power**

**Tip 1:**

When applying the Principle of Conservation of Energy, many students like to just apply the equation K.E. = P.E.

Although this may give the correct answer in simple problems, the precise form of the equation should be:

Gain in K.E = Loss in P.E. (for a falling object) ........ (1)

Loss in K.E. = Gain in P.E. (for a rising object) ........ (2)

For example, if an object initially travelling at 6m/s rolls down from the top to the bottom of a frictionless slope, and descends a vertical distance of 8m, what is its velocity at the bottom of the slope?

Using equation (1) above:

Gain in K.E = Loss in P.E.

½ *m* *v*_{bottom}^{2}
- ½ *m* *v*_{top}^{2} = *mgh*

½ *m* *v*_{bottom}^{2}
- ½ *m* (6)^{2} = *m* (10) (8)

½ *v*_{bottom}^{2}
- ½ (6)^{2} = (10) (8)

*v*_{bottom} = 14 m
s^{-1}

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