2 Hour Physics

A base (or fundamental) quantity is?

It is one that cannot be expressed as another quantity, e.g. length, time.

A derived quantity is one that is?

It a combination of base quantities. e.g. 'speed' is distance per unit time.

LIST ALL THE BASE QUANTITIES AND THEIR UNITS

• Length (L), unit \= m
• Mass (m), unit \= kg
• Time (t), unit \= s
• Current (I), unit \= A
• Temperature (T), unit \= K
• Amount of a substance (n), unit \= mol
• Luminous intensity (lv), unit \= candela (cd)

LIST ALL THE DERIVED QUANTITIES AND THEIR UNITS

Area (A), unit \= m² (m x m)
Volume (V), unit m³ (m x m x m) \=
Pressure (P), unit \= Pa (N/m²)
Force (F), unit \= N (kg m/s²)
Charge (Q), unit \= C (A x s)

Length Measuring Instrument

Metre rule

Mass Measuring Instrument

Scale balance

Time Measuring Instrument

Stopwatch

Electronic Current Measuring Instrument

Ammeter

Temperature Measuring Instrument

Thermometer

Volume Measuring Instrument

Measuring cylinder

Force Measuring Instrument

Spring balance

Speed Measuring Instrument

Ticker tape timer

Pressure Measuring Instrument

Barometer

LIST ALL THE Prefixes AND THEIR UNITS

Micro (u) \= 10^-6 (÷ 1,000,000)
Milli (m) \= 10^-3 (÷1000)
Centi (c) \= 10^-2 (100)
Kilo (k) \= 10^3 (x 1000)
Mega(M) 10^6 (x 1,000,000)

What is a Scalar?

A Scalar is a quantity that has magnitude but NO direction.

What are examples of scalars?

distance, speed, area, volume, density

What is a Vector?

A Vector is a quantity that has BOTH magnitude and direction.

What are examples of Vector?

Displacement, velocity, acceleration, force, momentum

How to calculate Parallel and antiparallel vectors:

1. When both arrows go same direction [ADD]
2. When arrows go in opposite direction [SUBTRACT]

How to resolve NON-PARALLEL VECTORS:

1. Use Pythagoras theorem
2. A \= Force 1, B \= Force 2, C \= Resultant

What is the unit of Mass?

kg

What is mass?

The amount of matter contained in an object. It is a measure of an object's inertia or resistance to change in motion.

What is the unit of Weight? N/Newton
What is weight?

The force exerted on a body's mass by gravity.

How to calculate weight?

Weight \= mass* gravitational force (10)

What is the centre of gravity of an object?

The centre of gravity of an object can be defined as the point at which the weight of a body acts

As it relates to centre of gravity of an object, what would give a higher stability?

Wide base (low centre of gravity)

Accuracy refers to?

how correct the data is.

Precision refers to?

how consistent the data is when reproduced between trials.

Avoiding parallax errors

These occur when the experimenter is not viewing the readings at eye level. When possible, equipment should always be placed on a level surface.

What is force?

Forces enable masses to overcome inertia, i.e. they are able to cause a change in an object's acceleration, deceleration or direction (even shape and size, but NOT mass)

What is force measured in?

Forces are measured in Newtons (N) which can be derived as 1N \= 1 kg m/s².

Type of Force

• GRAVITY
• WEIGHT
• FRICTION
• BUOYANCY / UPTHRUST
• ELECTROSTATIC
• MAGNETIC
• REACTION
• TENSION
• CENTRIPETAL
• NUCLEAR

GRAVITY

Pulls objects towards the centre of the Earth.

WEIGHT

The effect of gravity on an object's mass.

FRICTION

The resistance an object experiences when rubbing a surface.

BUOYANCY/UPTHRUST

The upward force exerted by a fluid.

ELECTROSTATIC

Attraction due to charged particles called electrons stored in an object.

MAGNETIC

An attraction or repulsion caused by north and south poles.

REACTION

The force that always acts opposite to another, e.g. the forward push from swimming while pushing the water backward.

TENSION

An upward force exerted on a string or rope attached to a load.

CENTRIPETAL

The pull towards a central point for an object moving in a circle.

NUCLEAR

The attraction holding the nucleus of an atom together.

What happens if a force is absent?

there will be no change in motion or direction.

The force of weight acts \____ from the centre of gravity.

Downward

Finish the statement, Objects or systems that are stable tend to -

have most of their mass deposited much LOWER than unstable ones. They are said to have a low centre of gravity.

What will happen to objects in a vacuum?

In a vacuum, objects (whether it be a rock or paper) will accelerate and fall at the same rate.

What will happen to objects in a air?

In air, the force of air resistance will affect falling speeds.

What are LEVERS?

They are simple machines that have an input and an output.

What is the input and output force of a lever called?

The input force is usually referred to as the EFFORT and the output as the LOAD.

This point of rotation on a lever is referred to as - ?

the PIVOT or FULCRUM.

First class levers placement

Fulcrum between effort and load.

Second class levers placement

Load between effort and fulcrum.

Third class levers placement

Effort between load and fulcrum.

The Principle of Moments states that:

THE SUM OF CLOCKWISE AND ANTICLOCKWISE MOMENTS ABOUT THE SAME PIVOT IS EQUAL AT EQUILIBRIUM.

Moment \=

Force x Distance Unit \= Nm
Calculating the effort, E:

Hooke's Law states that:

The extension of a spring is directly proportional to the force acting on it, given it is within its elastic limit.

Hook’s law Formula

F \= kx
F \= Force (N)
x \= extension (m)
k \= spring constant (N/m)

What is the elastic limit?

The elastic limit of a spring is within the limit of proportionality between force and extension. If too much force is applied, the spring can experience permanent deformation.

Define density

Density is defined as mass per unit volume.

What is density SI unit?

The SI unit is kg/m³.

Formula for density?

P \= m/v
P \= density
M \= Mass
V \= Volume

When does Floating occurs?

If an object's buoyant force is greater than its weight, or if it is less dense than its medium.

More surface area \=

object more likely to float

When does Sinking occurs?

If an object's weight is greater than its buoyant force, or if it is denser than its medium.

What is Relative density?

It is a given ratio of the density of a substance in reference to the density of the medium.

Relative density formula

R.D. \= Density of oil/ Density of seawater

Archimedes' Principle states that:

The upward buoyant force that is exerted on an object immersed in a fluid is equal to the weight of fluid displaced.

What is Distance?

Distance is how much ground an object has covered despite direction. It is a scalar.

What is displacement?

Displacement is the overall change in position of an object in a straight line between its origin and destination. It is a vector.

Difference between Distance and Displacement

Displacement is the shortest distance and distance is the total path covered.

In the displacement-time graph what represents the gradient?

Velocity

What is speed?

Speed is distance per unit time. It is a scalar.

What is velocity?

Velocity is the displacement per unit time. It is a vector.

Formula for Speed

= distance / time

Formula for Velocity

= displacement / time

Unit for velocity

m/s

What is acceleration?

Acceleration is a change in velocity over time.

Acceleration unit

m/s².

Acceleration formula

a \= (v-u)/ t
v \= final velocity
u initial velocity

In the velocity-time graph, the gradient represents

acceleration.

In the velocity-time graph, the displacement travelled is represented as?

the area under the graph.

Newton's 1st Law

An object at rest remains at rest, or an object in motion remains in motion at a constant velocity, unless an unbalanced force acts upon it.

With no outside forces, a stationary object will

not move

With no outside forces, a moving object will

not stop

Newton's 2nd Law

The force on a body is directly proportional to its acceleration. (F \= ma)

Newton's 3rd Law

• Every action force has an equal and opposite reaction force.
• If a Body A acts on Body B, then B exerts an equal and opposite force on A.

What is Linear momentum (p)?

Linear momentum (p) is the product of mass and velocity for an object travelling in a straight line.

What is Impulse?

Impulse is the force that produces a change in momentum.

Momentum Formula

\= mass x velocity
p \= mv
p\=Fxt

Momentum Unit

kg m/s or Ns

The law of conservation of linear momentum states that:

With no external forces, the total momentum before collision is equal to the total momentum after Collision.

What is energy?

Energy is simply defined as the capacity for doing work. The SI unit for energy is Joule (J).

What is a Joule?

A Joule is defined as the work needed to move 1N by a 1m distance, so 1J \= 1Nm.

The law of conservation of energy states that:

Energy can neither be created nor destroyed. It can only be converted from one form to another.

Some types of energy:

• Chemical, e.g. batteries, fuel
• Kinetic, e.g. moving car, falling water
• Gravitational potential, e.g. boulder on cliff
• Elastic potential, e.g. compressed spring
• Thermal, e.g. fire
• Electromagnetic, e.g. sunlight
• Nuclear, e.g. fission reactors

What is work?

Work is energy used to produce some type of mechanical change.

What is work Measured in

Joules (J).

Formula for Work

W \= F x d
d \= distance (m)
W \= Work (J)
F \= Force (N)

What is Power?

Power is the rate of energy conversion.
What is Power Measured in

Formula for Power

P \= E/T
P \= Power (W or J/s)
E \= Energy (J)
t \= time (s)