Cp13 forces and matter

3 types of forces on an object

stretching, compressing, bending

If you want an object to stay still…

you have to apply more than one force

deformed

when an object changes shape

2 different types of deformation

elastic and inelastic

Force and extension are…

Directly proportional

extension

the increasing length of a spring when it’s stretched

when you hang a spring from a solid surface…

the spring exerts a force downwards due to its weight, the solid surface exerts and equal and opposite force upwards

As force is doubled…

Extension doubles

You can tell that force and extension are directly proportional on the graph as..

The graph is a straight line through the origin

how much a spring extends

depends on the spring constant

The gradient of a line on the graph is the…

Spring constant

spring constant equation

f=ke

spring constant

how many newtons it would take to stretch the object by 1m

the higher the spring constant…

the stiffer the spring

Elastic

The object will return to its original shape when forces are removed

Inelastic

Objects will keep their new shape after the forces are removed

Some objects are —— when the forces are small, but behave —— when the forces are big

Elastic, inelastically

If the forces used to stretch springs are too big, they can become…

Permanently deformed

Extension of an object

The change in length when forces are applied

There is usually a — relationship between the force and the length

Linear

The relationship between the force and length of a spring becomes —— if the spring is stretched too far

Non linear

To stretch an object…

You need more than one force and one end must be fixed

Hookes law

The extension of a spring is directly proportional to the force applied, up to the limit of proportionality

Hookes law equation

Force= Spring constant x extension

Spring constant equation (gradient)

Force/extension, change in y/change in x

Rubber bands don’t obey Hookes law as…

The force and extension aren’t in direct proportion

Work done

The energy transferred when a force moves through a distance

Work done equation

Force x distance

Energy transferred in stretching a spring equation

1/2 x spring constant x extension squared