Physics - Forces and Matter

elastic vs inelastic distortion

E - returns to original shape if forces removed

I - keep new shape if removed

extension

change in length when forces r applied

spring constant

a measure of the stiffness of a spring up to limit of proportionality

higher the spring constant=stiffer

Limit of proportionality (elastic limit)

hookes law no longer applies

force n extension r no longer DP

hookes law

Extension is directly proportional to force until the spring reaches it's elastic limit

elastic limit

maximum deformation of elastic distortion

force extension graphs

below limit of P :

linear extension+elastic distortion+gradient=spring constant

energy transferred in streching

- work done when extended/compressed

- epe in spring (w.out inelastic distortion, wd=epe)

investigating springs PRACTICAL

1. measure length of springs w no weights n measure length

2. hang 1 newton (record extension)

3. repeat 10 times

4. repeat 1-3 w diff spring

5. use spring constant equation

investigating springs APPARATUS

- clamp stand

- 2 bosses, 2 clamps

- spring (top clamp)

- ruler (bottom clamp)

pressure

Force per unit area.

fluid pressure

exerts pressure at a point below its surface due to weight of fluid above that point

fluid

liquid or gas

fluid pressure increases with...

• depth (more weight so greater force)

• density (of fluid)

• gravity

(not surface area - pressure at bottom is equal - remeber that thing with the weird shaped test tubes but in the end all same level)

Why does atmospheric pressure decrease with altitude?

increasing altitudes means that...

- no of air molecules decreases

- weight of air increases

- less air above a surface

also , pressure increases with increasing depth

pascal

unit of pressure Pa

pressure causes..

a force normal (perp) to surface

pressure in a fluid due to fluid and AP

AP due to depth of A above

water more dense than air at sea level

so deeper you go, more pressure

why does fluid pressure depend on density and depth

- pressure depends on weight of fluid above

- deeper = more weight

also,

fluid with greater density = same vol of fluid ab has greater weight

why is an object in a fluid subject to upthrust

more pressure from bottom than above (resultant force up)

upthrust and displacement

upthrust= weight of water displaced

floating

upthrust equal to weight of object

e.g. jump into pool = your weight greater than weight of displaced water

sinking

upthrust less than weight of object

density of object greater than fluid it will sink