A Level Physics Module 2 - Foundations of Physics

Physical Quantity

Property of an object that can be measured

Base units of SI

Metre, kilogram, second, ampere, kelvin, mole, candela

Base unit of length

Metre

Base unit of mass

Kilogram

Base unit of time

Second

Base unit of electric current

Ampere

Base unit of temperature

Kelvin

Base unit of amount of substance

Mole

Base unit of luminous intensity

Candela

Derived units

Units that can be worked out from the base units and equations linking base units together.

Unit of force

Newton

Symbol for Newton

N

Newtons expressed in SI units

kg m s^-2

Unit of pressure

Pascal

Symbol for Pascal

Pa

Pascals expressed in SI units

N m^-2

Unit for energy/work done

Joule

Symbol for Joule

J

Joule expressed in SI units

N m

Unit for power

Watt

Symbol for watt

W

Watt expressed in SI units

J s^-1

Unit for electrical potential difference

Volt

Symbol for volt

V

Volt expressed in SI units

J C^-1

Unit for electrical resistance

Ohm

Ohm expressed in SI units

V A^-1

Unit for electric charge

Coulomb

Symbol for Coulomb

C

Coulomb expressed in SI units

A s

Unit of frequency

Hertz

Symbol for Hertz

Hz

Hertz expressed in SI units

s^-1

How to convert from celsius to kelvin

Add 273

How to convert from kelvin to celsius

Take away 273

How to convert from Fahrenheit to celsius

Subtract 32, multiply by 5, divide by 9

Scalar quantities

Quantities with size but no direction

Examples of scalar quantities

Length, mass, time, speed, temperature, volume, energy, potential difference, power

How to add scalar quantities

Addition?

What must be the case to add/subtract scalar quantities?

Same unit

Difference between adding/subtracting and multiplying/dividing scalar quantities

They don't have to be in the same unit when you are multiplying or dividing.

Vector quantities

Quantities with direction and magnitude

Examples of vector quantities

Displacement, velocity, acceleration, momentum, force

Difference between distance and displacement

Distance is scalar, displacement is vector

Why is the magnitude of displacement always equal to or less than the distance?

Displacement is the direct distance between two points so it is always either less than or equal to the distance.

How is a vector quantity represented pictorially?

A line with a single arrowhead.

How to find the resultant vector from parallel vectors

Add them together

Parallel Vectors

Vectors that act in the same line and direction

How does a resultant force differ from the parallel vectors making it up?

The magnitude will be greater

How is the resultant force the same as the parallel vectors making it up?

Same direction

Antiparallel Vectors

Vectors that act in the same line but in the opposite direction

How to find the resultant force from antiparallel vectors

Make one of them (It doesn't matter) negative and then add them together

Perpendicular Vectors

Vectors that act at right angles to each other

How to find the resultant force of perpendicular vectors

Pythagoras' Theorem

How to find the direction of a resultant force of perpendicular vectors

Use tan (Trigonometry)

Resolving the vector

Splitting it into two perpendicular components

Equation for vertical component of a vector

F x sintheta

Equation for horizontal component of a vector

F x costheta

How to find the resultant force of non-perpendicular vectors

Cosine rule

Cosine rule

a2 = b2 + c2 - 2bccostheta

How to find the direction of the resultant force of non-perpendicular vectors

Sine Rule

Sine rule

a / sinA = b / sinB

How to subtract vectors

Reverse the direction of one of the vectors, making it negative, and add to the other.