Forces and Moments Flashcards
Weight
Measure of the force of gravity acting on an object, measured in Newtons
Mass
Measure of the amount of matter that makes something up, measured in kilograms
Equation for weight
Weight= mass x gravity
Moment
Object placed on pivot
Applied force can have turning effect- this is a moment
Amount of turning effect depends on the size of the force and distance from the pivot
Moment equation
Moment= force x perpendicular distance
Newtonmeters Newtons Metres
Principle of moments
When a system is in equilibrium (balanced) the moments are equal:
The sum of the clockwise moments = sum of the anti-clockwise moments
Lever
Simple machine which uses a pivot
How do you make a task easier?
Increase the distance between the pivot and effort
Centre of mass
Mean position of mass of object
Where object’s weight appears to act
Lower centre of mass, the more stable the object
Symmetrical objects’ centre of mass always on axis of symmetry
Stability
For an object to be stable, its centre of mass must be above the area between supports. To increase stability you can:
- Lower centre of mass
- Create a wider base
Deformation
Elastic materials change shape when.a force is exerted on them e.g spring
Stretch when pulled
Compression when squashed
Greater force exerted = greater deformation
(Elastic band gets longer the harder you pull it)
Hooke’s law
The extension of a spring is directly proportional to the force applied
Extension= total length when stretched- original length
FORCE= SPRING CONSTANT x EXTENSION
CONSTANT= FORCE ➗ EXTENSION
Elastic limit
Elastic if it will return to its original size/shape when stretching force removed
Plastic material will be permanently deformed when force is applied
It will not return to the original size and shape
ELASTIC LIMIT is the point at which it will stop behaving like an ELASTIC and start behaving like a PLASTIC
Will be PERMANENTLY DEFORMED when stretching force is removed.
As soon as line in graph stops being directly proportional, entering plastic region
