A.2 Forces

Question 1

what is fluid resistance?

Answer 1

opposition to motion through fluid

Affected by viscocity, velocity, density, and surface area.

Question 2

what is terminal velocity?

Answer 2

forces are balanced and therefore velocity is constant

• affects flight path of projectiles- not parabolic, lower max height, lower range, steeper fall than rise, time taken to hit floor decreases

Question 3

what is a force?

Answer 3

• vector quantity
• causes change in shape
• causes acceleration
• measured in Newtons N

Question 4

what is a free body diagram?

Answer 4

all forces acting on a single body/object from a single point

If a closed room it means it is equilibrium

Question 5

what is elastic force?

Answer 5

• restoring force back to equilibrium position
• not only springs and bands elastic
• proportional to extention

Question 6

what is Hooke’s law?

Answer 6

F=-kx
Force and extention are directly proportional until the limit of proportionality

ELASTIC BAND does not obey hookes law- not a straight line (look at notes)- area tells us work done in stretching vs unloading

Question 7

what is the elastic limit?

Answer 7

• if stretched beyond, object will not return to original shape when force is removed
• this is called plastic/permanent deformation

Question 8

what is friction?

Answer 8

• force that opposes motion between two surfaced
• static= force applied but no motion
• dynamic= constant- less than static

coefficient of friction= μ

Question 9

what is drag?

Answer 9

a frictional force caused by motion through a fluid
factors:
- speed- f=kv for small, slow moving objects, and f=kv^2 for large, fast moving objects
- nature of fluid- density, viscosity
- shape of object
- nature of surface of object.

Question 10

what is viscosity?

Answer 10

• resistance of fluid to motion of objects through it
• resistance of the fluid to flow
• greater viscocity = greater drag force

for a sphere radius r

symbol= η

mg=ρ4/3πr^3+6πηrv