Forces, density and pressure

what is center of gravity

Point at which the whole weight of the object may be considered to act

what is a moment of a force

turning effect of a force

what is the only force which when applied is one to stop the obejct falling

object at the pivot

what is a fulcrum

a fixed point about which a level turns

what happens to the turning effect when the rule approaches the vertical position

becomes smaller

what happens to the turning effect when the rule goes further from the vertical position

becomes larger

what is a moment of a force in terms of its formula

product of the force and the perpendicular distance at the line of action of the force from the pivot

what is the formula for moment

F x perpendicular distance

what are couples

two forces, equal in magnitude, but opposite in direction whose lines of action do not coincide

where are forces applied in couples

two forces of equal size but opposite direction on opposite sides

why do we not say “moment of a couple”

couples are produced by two forces while moments are caused by one

what is the torque of a couple

product of one of the forces and the perpendicular distance between the forces

how do you calculate couples

F x distance between forces

what is the unit for moment

N m

what is the unit for couples

N m

what is the principle of moments

the total sum of clockwise moments about an pivot is equalt to those of the anticlockwise moment

what is said makes an object have rotatiional equilibrium

an object with no tendency to change its speed of rotation

what is rotational equilibrium

state in which an object is perfecty balanced in terms of rotation

what is rotational equilibrium in terms of torque

no net torque

what is torque

turning effect produced by a force acting at a distance from a pivot

how do you find torque

f x perpendicular distance

what is equilibrium

cannot be any resultant force in any direction

how would you show equilibrium in a vector diagram

forces form a close shape

what is equilibrium

no net forces

no net moment

what is density

mass per unit volume

what is the unit for density

kg m ^-3

what is pressure

mass per unit area

what is the unit for pressure

N m ^-2

how does pressure change when an object goes deeper in a fluid

increases with depth

what is the proportionality between pressure and depth

direcly proportional

if there is atmospheric pressure, how do you find pressure of something below the surface of a fluid

sum of external pressure and pressure due to depth below the surface of the liquid

what is the unit for torque

N m

what is Archemedes’ principle

upthrust acting on an object immersed in a fluid is equal to the weight of the fluid

what is the difference between torque and moment

no difference

how does an object provide an upthrust

object in full immersion

an object fully immersed, what is the difference in pressure at the bottom of an obejct and the top of an object

greater pressure at the bottom than at the top

how do you find buoyance force

pressure x volume x gravity

if a force is not perpendicular to the distance from the pivot, what must you do

find the component of the force that will make it permendicular