Measuring Force

We can measure a force and we use a specific unit to do so. It is called a
*Newton*. This measurement is called an *SI UNIT*, which stands for
Systeme International. This means it is an internationally recognised term for
a whole range of metric measurements which was accepted in 1960.

Mass

Mass is represented by *m* in science - but what is it? It is the amount
of matter in an object.

Imagine looking at a piece of ordinary chocolate and an a piece of Aero. If the two pieces were exactly the same size and you were to predict which would be the heavier I am sure you would go for the ordinary chocolate. This is because, for the same size, the matter in it is more closely packed. You could say the same about a piece of polystyrene and a block of wood of exactly the same volume, or any number of other materials.

When we want to measure Mass we do so using *grams *or *kilograms*.
For some this can cause confusion because we normally associate grams or kilograms
with weight. BUT as we have said earlier *Newtons* are used to measure
Force, and since Weight is a downward force caused by Gravity, weight is measured
in *Newtons*

It should also be remembered that the Mass of an object is constant whereas the weight of an object can change in Gravity, and this will be affected by where the object is in relation to other objects. For instance, your weight on the Moon would be approximately one sixth of your weight on earth due to the effect of Gravity.

Speed

Speed is the rate at which an object moves in a straight line or in a continuous curve.

If we wish to find out the speed of an object and we know the distance travelled and the time taken we can use the following formula:

SPEED = | DISTANCE |

TIME |

For instance, if we know the distance travelled is 180 kilometres and the time taken is 2 hours then:

SPEED = | 180 km/h |

2 hrs |

SPEED = 90 km/h

Similarly we can use the formula to find out other aspects:

DISTANCE = SPEED TIMES TIME

AND

TIME = |
DISTANCE |

SPEED |

Velocity, Acceleration

Balanced Forces

Forces that oppose motion

What children might say or think about forces

Self assessment