P1 & P2 Triple Content

moment of force

the turning effect of the force about a pivot that an object can rotate around

lever

increases distance from the pivot to allow for less effort for same amount of load

• it rotates around the pivot

equilibrium

when something is balanced

The principle of moments

If an object is balanced, the total clockwise moment is equal to the total anti-clockwise moment.

• forces are perpendicular to the distance from the pivot

• F₁d₁ = F₂d₂

pivot diagram

Moment equation

Moment(Nm) = Force(N) x Distance perpendicular from the pivot(m)

work done but measured in Nm & distance perpendicular from pivot

mechanical advantage

a measure of how many times force is multiplied to fulfil a task

mechanical advantage equation

load(what is lifted) / effort(force exerted)

gears

consists of wheels with toothed edges that rotate on an axle/shaft that acts as the pivot

properties of the gear

• the teeth of one gear fits into another’s, meaning they can turn each other

• the teeth all move in the same direction HOWEVER, one gear moves clockwise, the other anti-clockwise.

diagram of gear’s operation

Force applied to gear is NOT moment

• different gear sizes changes the distance from the pivot, as a larger gear has a force that acts further

• larger = larger force. smaller = smaller force

gear ratio

tells you the number of times drive gear must turn to turn the driven once

gear ratio equation

driven gear’s number of teeth / drive gear’s number of teeth

pressure

the concentration of a force or force per unit area

pressure equation

pressure(Nm or Pa) = Force(N) x area(m²)

pressure in liquid

• pressure is exerted evenly across the whole surface in all directions

• force is only exerted perpendicularly to each surface

(only when submerged at a specific depth)

hydraulics

a machine that uses liquid to transmit a force

• as pressure in a liquid is the same everywhere, force from one piston lifts the other as pressure remains balanced(and increases)

hydraulic pressure equation representation

P₁ = P₂

F₁/A₁ = F₂/A_{2 (equation for pressure)}

F₂ = F₁ x (A₂/A₁) _{(mechanical advantage)}

atmospheric pressure

the force exerted on a surface by the weight of the air column above it, caused by the collisions of air molecules

• pressure decreases higher up as there’s less molecules, meaning less weight.

atmospheric pressure equation

Weight = density x gravity x volume(h*w*l)

atmospheric pressure equation units

volume = m³

density = kg/m³

gravity= N/kg

liquid pressure

when an object is immersed in a liquid, it is exerted evenly across the whole surface of the object in all directions

liquid pressure factors

pressure at a point increases with height of column(weight) above it

• more density means higher weight= higher pressure

liquid pressure equation

pressure = height x density x gravitational field strength

liquid pressure equation units

pressure = N/m² / Pa

height = meters

gravity = N/kg³

density = kg/m³

upthrust

caused by difference in pressure between top and bottom of the object

• submerged object experiences greater pressure on bottom surface than top surface

requirements of upthrust

if one force is larger than the other, the object will sink

• if the object is less dense than the fluid density, it’ll float as it will never displace enough fluid to hold its weight

Boyle’s law

as volume decreases, particles collide more frequently and pressure increases

• gas pressure is inversely proportional to volume, this is Boyle’s law

Boyle’s law equation(volume pressure relationship)

pressure₁ * volume₁ / temperature₁

= after change

pressure₂ * volume₂ / temperature₂

Rearranging Boyle’s Law

as the equation is constant, removing whichever element is fixed

• rearrange the equation and solve with values available