## Useful Things Worth Knowing

The pressure of a column of gas or liquid is independent of the area. This is becauseand the area is not mentioned.

In the absence of air resistance, a feather falls with the same acceleration as a cannon ball.

Hence if both are released from the same height at the same time, they will reach the ground at the same time.

If you double the speed of a car, you don't double the braking distance. You multiply by 4. If the speed of the car is tripled the stopping distance is multiplied by 9. This is because

Silver/shiny things heat up more slowly than black/dull things because they are worse at absorbing radiation. Silver/shiny things cool down more slowly than black/dull things because they are worse at emitting radiation.

The resistance of a thermistor or semiconductor decreases if the temperature increases. If the thermistor is in a circuit with a voltage, then the current in the circuit may increase and the voltage across the thermistor may decrease.

Materials with higher specific heat capacities take long to heat up and heat up less for the same amount of energy.

Materials with higher latent heats of vapourization or fusion need more energy to evaporate or melt.

Less of the material is evaporated or melted for the same energy input.

Friction is always present. If energy is lost during a process it is usually because work has to be done to overcome friction or air resistance.

When anything is melting or evaporating the temperature is constant.

IfthenandBE SURE YOU LEARN HOW TO REARRANGE THESE SIMPLE EQUATIONS.

The distance travelled is equal to the area under a velocity time graph. The acceleration is equal to the gradient of a velocity time graph.

Heavier things take longer to slow down than light things, if the braking or resistance force is the same. This means they will travel further before they stop.

A moving magnet will make charge move and produce a current and a moving charge – a current – will induce a magnetic field.