Mass and Weight
- Mass is the amount of matter in an object.
- It is measured in kg.
- Weight is a force.
- The weight of an object depends on the mass of the object and gravity
- weight is measured in newtons.
MASS X 10 = WEIGHT
Centre of gravity
The centre of Gravity of an object is the point through which all the object's mass or weight appears to act.
To find the centre of gravity for a rectangle or any regular shaped obect draw digonals across it - where they intersect is the centre of gravity.
Levers and Moments
objective: to understand how levers work and what is ment by a "moment"
- A lever is a device to help you complete a task.
- all levers have a pivot and its position relative to the effort force and the load force determines how easily the lever enables us to carry out a task.
- the closer the pivot is to the load force the less effort force is needed.
The moment / turning effect depends on three things:
- The distance from the pivot
- the effort force
- the angle of force.
Moment = FORCE X DISTANCE FROM PIVOT
Force is measured in Newtons
Distance is measured in cm, m
Moment is measured in Ncm, Nm
Principle of moments
Objective: To understand what the "principle of moments" is.
For a system to balance, the clockwisew moments must be equal to the anticlockwise moment.
Objective: to understand what is menat bythe stability of an object.
Two features that control the angle of toppling are:
- The height of the centre of gravity
- the area of the base
A low centre of gravity and a large base will prevent toppling.
if the centre of gravity is higher up, when tilted, the weight will act outside the object sooner.