# P2.3 (1) - forces in action Flashcards

## p2.3.1 - p2.3.3 (spec approved)

what are elastic bodies?

objects that return to original shapes when the deforming force is removed

what are plastic bodies?

objects that do not return to their original shape when the deforming force is removed

state hooke’s law

the extension of a body is directly proportional to the force applied, as long as the limit of proportionality is not exceeded

what is the equation for hooke’s law?

force = spring constant x extension (N) = (N/m) x (m)

F = K x E

how can the spring constant be found from a force-extension graph?

from the gradient

where does the limit of proportionality lie on an extension-force graph?

just before it begins to curve

what is the elastic limit?

the like middle point

- if exceeded, spring is permanently deformed (even when force is removed)
- below limit, spring returns to original length

where is the elastic limit on a force-extension graph?

just after the limit of proportionality

what is the spring constant a measure of?

the stiffness of a spring

if a spring is very stiff, how is the spring constant?

higher

what is the equation to figure out the work done while stretching a spring?

energy (J) = 0.5 x spring constant (N/m) x (extension (m))^2

what is the work done while stretching a spring also known as?

elastic potential energy

can you use an elastic band instead of a spring when using a newton-meter, and why?

no, as it does not obey Hooke’s law (as it has a non-linear relationship between force and extension)

why is a rubber balloon hard to blow up at first (picture graph in your head)?

as rubber does not follow hooke’s law.

so at the beginning the gradient is very high, meaning more force is applied to increase its extension

describe the relationship between glass and force and extension

it has a linear relationship (straight line), but a very steep gradient - as it is a stiff material