# Stretching Springs/Hookes Law.

## Mustafa Rafik

10.7Api

Science coursework

Title:

Stretching Springs/Hookes Law

#### Scientific knowledge

A force is able to change the shape of an object, the more the strength and force you apply, the more the shape of the object will change because the particles of the object are being moved therefore it will change the shape of the object because of the particles being pushed for e.g.

A force is also able to change the motion of the object.

The force, which is applied to the object, makes the object stay in that shape which is the cause of the   force hitting the object and making it change, this will not go back to its original shape like shown in number 2, this is because the particles have been hit so hard that the attraction of the particles which makes them go back to its original shape have been damaged so it will then go into another shape.

##### Elastic material

This is a material that will stretch and go back to normal, its original shape.

Elastics behavior is the ability of a solid to regain its shape when the external forces are removed.

###### What is Hookes Law?

Hokes Law is a rule for a spring,

‘For a spring-that for a helical spring or other elastic material the extension is directly proportional to the applied force provided the elastic limit is not exceeded’

This means that the extension is directly proportional to its force until its elastic limit.

The graph or load against extension is a straight line.  When the load is doubled, the extension doubles, this relationship is known as one of direct proportional.

This result is in agreement with Hookes Law.  This law is named after Robert Hooke who first the relationship between the amounts of stretch in objects compared to the load force acting on the object.

This graph shows the increase in length of an elastic wire as the stretching force on it increases. Over the straight-line part of the graph there is a 10-mm increase in length for every extra Newton (N) of applied force. The change in length (strain) is proportional to the force (stress), a relationship called Hooke’s law. The wire begins to stretch disproportionately beyond an applied force of 8 N, which is the wire’s elastic limit. When this force is removed, although the wire will decrease in length somewhat, it will not go back to its original length.

What happens to a spring when forces are added to it?

When a string is stretched and then released it returns to its original shape and length, however this is only in use if the spring isn’t overstretched.

An overstretched is noticeable and can’t be returned to its original position because the coil pulls out and it changes the shape of the coil and so can’t return to normal when the force is taken off due to the attraction particles being pulled apart.

As the force increases the spring increases until it has a point where it goes past its elastic limit.

When we put weight on the spring it expands due to the particles being pulled and then expanding.

When we apply a force the spring expands, the spring works by forces of attraction between the particles.

Patterns we expect to see

The patterns we expect to see are as the weight increases the length of the spring should increase because the particles are being stretched more and more so the spring will go bigger and bigger.

Elastic limit of a spring

The elastic limit is a point which the spring becomes deformed and at a point where the amount of stretch is no longer directly proportional to the load.  The spring will be deformed and will no longer return to its original length.

This is because the particles have been stretched too much and can’t stretch any more because the attraction between the particles have been damaged due to the overstretching, therefore this will then not return to its original place.  Also the external force applied to a material creates stress within the material; this stress causes the material to deform.

Elasticity (physics ), property of a material that causes it to            resume its original size and shape after having been compressed or stretched by an external force. An external force applied to a material creates stress within the material; this stress causes the material to deform. The amount of deformation, as a fraction of the original size, is called strain. For many materials, including metals and minerals, stress is directly proportional to strain over a certain range of these quantities. This relationship is known as Hooke’s Law after the British physicist Robert Hooke, who first expressed it. However, ...