4.5.3.0 - Forces and elasticity

What can happen do an object when you apply a force to it?

When you apply a force to an object, you may cause it to bend, stretch or compress

However, what is needed for an object to not just be displaced by a force?

For an object to be stretched, compressed or bent you need more than one force to be acting on the object

(otherwise it would simply be displaced)

What is meant by if an object has be ‘elastically deformed’?

An object has be elastically deformed, if it can go back to its original shape and length after the force has been removed

Objects that can be elastically deformed are called…

…. elastic objects

What is meant by if an object has been ‘inelastically deformed’?

An object has been elastically deformed if it doesn't return back to it’s original shape and length after the force has been removed

Objects that can be inelastically deformed are called…

… inelastic objects

When a force stretch or compresses an object, what is done and what does it cause?

Work is done when a force stretches or compresses an object

This causes energy to be transferred to the objects elastic potential energy store of the object

How much energy is transferred to the elastic potential store if an object is elastically deformed?

If the object is elastically deformed, all this (from the force doing work) energy is transferred is transferred to the objects elastic potential energy store

What is the relationship between the extension of an object to the force applied?

The extension of an object is directly proportional to the force applied

However, the extension of an object is only directly proportional to the force applied , given what?

The extension of an object is only directly proportional to the force applied , provided that the limit of proportionality is not exceeded

What does the spring constant depend on?

The material

Does a stiffer spring have a greater or lower spring constant?

A stiffer spring has a greater spring constant

Give the equation use to calculate the force on a stretched / compressed object.

Force = spring constant x extension

F = Ke

Give the units for all the components of this equation.

Force - in newtons, N

Spring constant - in N/m

Extension - in metres, m

Give the equation for calculating the work done / energy transfer to an objects elastic potential as it’s deformed.

Elastic potential energy = 0.5 x spring constant x extension (squared)

Give the units of all the components in the equation.

Elastic potential energy - in joules , J

Spring constant - in N/m

Extension - in metres , m

What is meant by the limit of proportionality?

Refers to the limit to the amount of force that you can apply to an object for the extension to keep on increasing proportionally.

Where is the limit of proportionality on a graph?

There is a maximum force above which the graph curves

This shows the extension is no longer proportional to the force