Phys Vocab

magnitude

size of a quantity

homogeneity

The SI unit must be the same on both sides of the equation

Random error

not predictable or constant, caused by human ability,

parallex error

not being at eye level and reading the scale wrong, can be averaged out

Systematic error

Occur due to faulty equipment , cannot be averaged out.

Absolute Uncertainty

+-(1/2 x resolution of measuring equipment)

percentage uncertainty

absolute uncertainty/measurement x 100

absolute uncertainty (repeats)

+-(1/2 x range of readings)

add absolute uncertainties

Adding/subtracting uncertainties

add percentage uncertainties

Multiplying/dividing uncertainties

Multiply percentage/fractional uncertainty by power

Raising to a power

High random errors

large range of measurements (accurate, not precise)

Systematic errors

peak of the graph displaced to the left or right (not accurate, precise)

resolution

the smallest change in the quantity being measured (input) of a measuring instrument that gives a perceptible change in the reading

scalars

Have a magnitude and a unit

length, area, volume, speed, mass, density, pressure, temperature, energy, entropy, work, power.

Vectors

Have a magnitude. unit, and a direction

displacement, velocity, acceleration, momentum, force, lift, drag, thrust, weight.

Distance

How many meters an object has moved while changing positions (scalar)

displacement

length of the gap between two points (vector)

relative velocity

the velocity of an object in relation to another

Vector components

The components (usually horizontal and vertical) of a Vector

SI base units

Elcectrical current (A), thermodynamix temperature (K), time (s), length (m), mass (kg), Luminous intensity (cd), amount (mol)

10^12

tera (T)

10^9

giga (G)

10^6

mega (M)

10³

kilo (k)

10^-1

deci (d)

10^-2

centi (c )

10^-3

milli (m)

10^-6

micro upside down n

10^-9

nano (n)

10^-12

pico (p)

Suvat equation (no initial velocity)

s = vt - ½at²

mass

The property of an object that resists a change in motion. The amount of matter in a substance

weight

the effect of a gravitational force on an object

Newton’s first law

An Object remains at rest or continues to move with a constant speed unless acted upon by a resultant force

Inertia

The Resistance to motion that an object has because of its mass

transational equillibrium

all forces on an object are balaced

Newtons second law

If an object experiences an external net force, it will accelerate such that F(net) = ma

equation for momentum(p, kgms^-1)

mass(m, Kg) x velocity (v, ms^-1)

momentum

a measure of how difficult it is to stop a moving object

Impulse

the change in momentum of an object when a force acts on it

Impulse (Ns) equation

mv - mu (mass x velocity- mass x initial velocity)

rate of change of Impulse (N)

(mv-mu)/t = F

Newtons third law

When an object exerts a force on a second object, the second object simultaneously exerts a force of equal magnitude and opposite direction on the first object.

Friction

contact force acting when surfaces contact each other. Acts in opposite direction of motion

Drag

Resistive forces when moving through a viscous fluid

Air resitance

drag force when moving through the air

Terminal Velocity

The drag force is equal to the weight force

smaller mass means what happens to the deceleration?

makes the deceleration larger

closed sytem

a coservation of momentum

one dimension

move and interact only in one straught line

elastic collision

momentum AND kinetic energy are conserved

Inelastic collision

ONLY momentum is conserved, Kinetic energy isnt.

perfectly inelastic collision example

Objects stick together

Perfectly elastic collision example

Objects move apart.

principle of moments

when clockwise and anticlockwise moments are balanced (no resultant torque), no rotation will occur

Torque

the turning effect of a force

Equillibrium

when the sum of all forces acting on an object and the sum of all torques acting on the object are zero

couple

Two equal and opposite forces can produce a turning effect

Centre of gravity

the single point through whic the weight of an object is considered to act

uniform object

Centre of gravity in the middle of the object

Density

the mass of a substance per unit volume

Volume

The quantity of space an object takes up

Pressure

a measure of how “concentrated” an applied force is (pressure = force per unit area)

Upthrust

A n object placed in a fluid experiences an upward force from the fluid

Archimedes principle

the upthrust on a body which is either partially or fully submerged in water is equal to the weight of the water displaced by the body.

decimal places of a metre ruler/ruler

1 d.p. in cm

decimal places of a micrometer

2 d.p. in mm or 2d.p in cm

decimal places of a stopwatch

2d.p in seconds

Energy

the ability to do work

Law of Conservation of Energy

Energy can neither be created nor destroyed but it can change from one form to another (transformed or transferred

Types of Energy

• Kinetic Energy

• Gravitational potential energy

• Electrical energy

• Sound Energy

• Light Energy

• Elastic potential Energy

• Nuclear Energy

• Chemical potential energy

• Thermal Energy

Chemical potential energy(stored)

stored in the chemical bonds within substances such as fossil fuels, bio gas, carbohydrates and fats

elastic potential energy (strain)(stored)

stored in an object whose shape has been changed in s reversible way, such as a stretched or comppressed spring.

gravitational potential energy(stored)

stored in a system die to the gravitational field between two objects

kinetic energy(stored)

stored in moving objects

nuclear energy(stored)

stored in the nucleus of every atom and transferred during radioactive decay, nuclear fission or nuclear fusion.

work

the transfer of energy from one form to another

Joule

the amount of work done when a force of 1 Newton moves an object a distance of 1 meter in the direction of the force

Conditions for work to be done

• There has to be a force and a distance moved

• Energy needs to be transferred

isolated system

conservation of energy

kinetic energy

the energy of moving objects

Gravitational potential energy

the potential energy an object has because of its height

Power

the rate of transfer of energy or the rate at which work is done

density of water

997 kg/m³

Hooke’s law

for an object under tension, the extension is proportional to the applied load, as long as the limit of proportionality is not exceeded.

spring constant (k)

determines how much force will be required to deform a spring. measure of stiffness

Limit of proportionality

Hooke’s Law does not apply past this point.

Elastic limit

The spring will behave as a plastic material and wont return to its original length when load is removed

Tensile force

causes an object to stretch/increase in length

Compressive force

causes an object to be compressed

Plastic behaviour

deforms and stays deformed when force is removed

elastic behaviour

returns to original shape when force is removed

Young modulus

a measurement for the stiffness of a material

Stress

a measurement of the tensile/compressive per unit cross-sectional area of the material

Strain

a measurement of the extension of the material as a proportion to the original length

Ultimate tensile strength

the ultimate stress a material can withstand before it breaks

Brittle

Material fractures before plastic deformation (Glass, ceramic)

Ductile

Material can withstand large plastic deformation without breaking (copper)

Polymeric

material made up of long repeating chains of molecules - no plastic deformation