What is an elastic object?

One that regains its shape when forces deforming removed

What is extension?

It is increease in spring's length from original length

Result from spring's extension aganist force applied

Straight line throigh origin

it is directly proportional

How to get line of proportionality

spring's extension aganist force applied

Apply too big of a force , line begins to curve

exceeded line of proportionality

Elastic objects have to obey what law?

Hooke's law

What does Hooke law states?

The extension is directly proportional to the force applied

provides limit to proportionality , not exceeded

Equation expressing Hooke's law

F - ke

F = force applied in newtons , N

k = spring constant in N/m

e = extension in m

What happens the stiffer the spring?

Greater its spring constant

What happens the elastic object is stretched?

Work is done and the elastic potential energy store of object increases

When does Hooke's law also applied to?

Elastic object when it is compressed

Steps to investigate stretch?

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- Clamp string at upper end and weight haanger to keep straight
- Measure original length of spring with metre ruler
- Add weights at the bottom and measure length
- Repeating this

To investigate stretch

what do you do when each weight added?

Subtract it from original length of stretched length to give extension