PHYSICS

‘MASTER-BLASTER’

• Speed, Distance, Time

• Newton’s Laws (Forces)

• Work & Energy

• Radioactivity

• Stars & Planets

Topic: Speed, Distance, time

𝑺𝒑𝒆𝒆𝒅 =𝑫𝒊𝒔𝒕𝒂𝒏𝒄𝒆

𝑻𝒊𝒎𝒆

Speed measured in m/s

𝑨𝒄𝒄𝒆𝒍𝒆𝒓𝒂𝒕𝒊𝒐𝒏 =𝑪𝒉𝒂𝒏𝒈𝒆 𝒊𝒏 𝑺𝒑𝒆𝒆𝒅

𝑻𝒊𝒎𝒆

acceleration measured in m/s2

Speed and Acceleration

Question(s):

1. A car travels 3km in 250

seconds. What is its

average speed?

3,000 / 250 = 12 m/s

2. A cheetah stalks an

antelope, moving at

1m/s. It then darts

forward in pursuit of the

antelope. After 3 seconds

it is moving at 28 m/s.

What is its acceleration?

(28 – 1) / 3 = 9 m/s2

Topic: Speed, Distance, timeDistance-Time Graphs

Topic: Speed, Distance, timeSpeed-Time Graphs

Topic: Speed, Distance, time

Thinking Distance is

the distance travelled

while reacting.

Affected by tiredness,

alcohol etc.

Braking Distance is the

distance the car travels

after the brakes have

been pressed.

Affected by tyres, road

etc.

Stopping Distance (= Thinking Distance + Braking Distance)

Topic: Newton’s Laws (Forces)

• Newton 1:

“A body stays in a state of rest or uniform motion in a

straight line unless acted upon by an external force”

• Newton 2:

(Resultant) Force = mass x acceleration

• Newton 3:

“When body A pushes on body B, body B pushes back on A

with equal and opposite force”

Newton’s Three Laws

W = m x g

(g=10 on Earth)

Weight & Mass

Topic: Newton’s Laws (Forces)

Question:

1. What is Mr Pearson’s weight on Earth if has a mass of 83.5kg?

W = 83.5 x 10 = 835N

Earth Moon

20N 3.2N

no resultant force = no change (no acceleration)

Resultant force = 500-500 = 0N

Will travel at constant speed

Resultant force = 600 – 400 = 200 N

Will accelerate forwards

Resultant Force

Topic: Newton’s Laws (Forces)

Question:

The rocket has a

thrust of 200,000 N.

It has a mass of

18,000kg.

1. What is the rocket’s weight?

180,000N

2. What is its resultant force?

200,000 - 180,000 = 20,000N

3. Calculate the acceleration

a= f/m = 20,000/18,000 = 1.1 m/s2

When Weight = Air Resistance there is

no resultant force. Speed (velocity) doesn’t

change. Terminal Velocity.

Terminal Velocity

Topic: Newton’s Laws (Forces)

Topic: Newton’s Laws (Forces)Terminal Velocity - Specified Practical

Topic: Work & Energy

• When energy is transferred from one object to another,

scientists say “Work is done”.

• Different types of energy are: kinetic, thermal, gravitational,

elastic, sound.

• The amount of work done can be calculated by:

Work Done = Force x Distance

Work Done

Question:

How much work is done by the

man pushing the box?

W.D. = F x D

W.D. = 10 x 2

W.D. = 20 Joules

Gravitational Potential Energy (GPE) Kinetic Energy (KE)

GPE = m g h KE = ½ m v2

(g=10)

Kinetic & Gravitational Energy

Topic: Work & Energy

Question:

A cyclist has a mass of 68kg and is cycling at

8 m/s. She then rides up a hill to a height of 3m.

1. What is her KE at the start?

KE = 0.5x68x82 = 2,176 J

2. What is her GPE at the top?

GPE = 68 x 10 x 3 = 2,040 J

3. Why has she got less GPE than KE?

Energy lost as heat because of friction

• Force = spring constant x extension F = kx

• Bigger spring constant (k) = stiffer spring

• Specified Practical

Springs

Topic: Work & Energy

[H tier] Work done in stretching a spring is the elastic energy that gets stored in the spring. It is ½ x force x extension:

• W.D. = ½ F x

• W.D. is also area under the force –extension graph

WD

• Force = spring constant x extension F = kx

• Bigger spring constant (k) = stiffer spring

Springs

Topic: Work & Energy

[H tier] Work done in stretching a spring is the

elastic energy that gets stored in the spring. It is:

• W.D. = ½ F x

• W.D. is the area under a force–extension graph

WD

Springs – Specified Practical

Topic: Work & Energy

Vehicle Safety & Efficiency

Topic: Work & Energy

Efficiency:

• Aerodynamic losses:

streamlined designs.

• Rolling resistance: correctly

inflated tyres & tyre material that

doesn’t heat when squashed.

• Idling losses: stop/start systems

• Inertial losses: lighter cars.

Car Safety:

These increase the distance

taken to stop. This reduces

the force on the person (by

doing work over a larger

distance)

Topic: Radioactivity

• Isotopes are atoms with the same number of protons but

different numbers of neutrons. E.g.

• Some isotopes are stable (last forever).

• Some isotopes are unstable and decay at random.

Atoms

49𝐵𝑒

410𝐵𝑒

This atom has:

9 nucleons

4 are protons

5 are neutrons

Nucleon number

Proton number

• Unstable isotopes can decay via alpha, beta or gamma.

• Alpha is a helium nucleus ( 24𝐻𝑒 or 2

4𝛼 )

• Beta is a fast electron ( −10𝑒 or −1

0𝛽 )

• Gamma is an electromagnetic wave (g)

• Ionising (most to least): alpha, beta, gamma

• Penetration and stopping:

a, b, g and Decay

Topic: Radioactivity

92235𝑈 → 90

231𝑇ℎ + 24𝐻𝑒

614𝐶 → 7

14𝑁 + −10𝑒

Background radiation comes

from many sources.

Radon gas comes from rocks.

Medical uses such as imaging

and treatment

Nuclear waste storage is a problem

because it stays radioactive

for thousands of years.

Uses of Radioactivity

Topic: Radioactivity

“Half-life is the time taken for the number of radioactive nuclei

to reduce to one half of its value”

Specified practical:

decay dice

Dice and Half-life

Topic: Radioactivity

Questions:

1. What is the graph’s half-life?

2. A sample has an activity of

600Bq and half-life of 3 days.

What’s the activity after 12

days?

600 300 150 75 37.5

Dice Specified Practical

Topic: Radioactivity

Topic: Stars & Planets

• Earth – moon

• Earth – Sun

• Solar System

• Sun – near Stars

• Galaxy

• Galaxy – Galaxy

• Universe

Scale of the Universe

Distances are measured in:

• Kilometres (km) e.g.

300,000km Earth to Moon

• Astronomical Units (AU)

e.g. Jupiter is 5.2 AU from

the Sun.

1AU = distance from sun to Earth

• Light Years (LY) e.g. Milky

Way is 100,000 LY wide

1 LY = distance light travels in one

year

Forming the Solar System

Topic: Stars & Planets

Gravitational forces cause the

gas/dust cloud to shrink,

creating.

This gas cloud has come from

a dead, large star that went

supernova. This means it

contains many heavy

elements.

The centre becomes the Sun.

Around this, left-over gas/dust

forms the planets.

Rocks gather closer to the Sun

(rocky planets) and gases

further away (gas planets).

The Solar System

Topic: Stars & Planets

Star; Planets; Dwarf Planets; Moons; Asteroids; Comets

Lives of Stars

Topic: Stars & Planets

Hertzsprung-Russell Diagram [H-Tier]

Topic: Stars & Planets

Hertzsprung-Russell Diagram [H-Tier]

Topic: Stars & Planets

1

2

3

Revision Planning – Know vs Do!• Every topic: what is knowledge and what is doing

• Knowledge is revision (flash cards, look-cover-check)

• Doing is practising (past questions – get feedback)

Newton’s Laws

KNOW

Quote the three laws

Know difference between weight and mass

No resultant force = no acceleration

Describe cake case experiment

DO

Calculate resultant force

Calculate using F=ma

Calculate using weight = mass x gravity

Apply the three laws to situations (eg rockets)

Exam Paper Breakdown

• 40% Numeracy / Calculations

• 20% Practical skills / knowledge

• 1x ‘6 mark’ QER question

• 40% ‘AO1’ – knowledge of physics (KNOW)

• 60% ‘AO2/3’ – applying & using physics (DO)

• Typically, a question from each topic area

Top Five Tips for success!

• Organise a revision timetable.

• Little & often with planned breaks and rewards.

• Find out what you don’t know or can’t do and

focus on these areas. Ask for help.

• Use a range of techniques, that suits you.

• Suitable environment to learn without distractions

(turn phone off and wait for a break/reward).

Be positive, it is never too late to

make a difference!