Y10 SEM1: SCI EXAM CHEAT SHEET

⚛ PHYSICS

Scalars vs Vectors

Scalar = size only

  • Distance

  • Speed

  • Time

  • Mass

Vector = size + direction

  • Displacement

  • Velocity

  • Acceleration

  • Force

Distance vs Displacement

Distance

  • Total ground covered

  • Scalar

Displacement

  • Start → finish position

  • Shortest path

  • Includes direction

  • Vector

Speed vs Velocity

Speed

speed = distance ÷ time


  • Scalar


  • No direction

Velocity

velocity = displacement ÷ time


  • Vector


  • Must include direction

⚠ EXAM TRAP:

Distance ≠ displacement

Speed ≠ velocity

Acceleration

Acceleration = change in velocity over time.

a = (v - u) ÷ t

Where:

a = acceleration
v = final velocity
u = initial velocity
t = time

Units:

m/s²

Formula Sheet

Average speed

speed = distance ÷ time

Rearrange:

distance = speed × time

time = distance ÷ speed

Average velocity

velocity = displacement ÷ time

Rearrange:

displacement = velocity × time

time = displacement ÷ velocity

Acceleration

a = (v - u) ÷ t

Rearrange:

v = u + at

u = v - at

t = (v - u) ÷ a

Newton's Second Law

F = ma

Rearrange:

F = force (N)

m = mass (kg)

a = acceleration (m/s²)
m = F ÷ a

a = F ÷ m

Newton's First Law (Inertia)

An object:


  • at rest stays at rest


  • in motion stays in motion at constant speed in a straight line

UNLESS an unbalanced force acts on it.

Keywords:

inertia
constant velocity
unbalanced force

Newton's Second Law

F = ma

More force → more acceleration

More mass → less acceleration

Same acceleration + more mass → more force needed

⚠ ALWAYS mention:

If mass stays constant, increasing acceleration increases force.

Newton's Third Law

Every action has an equal and opposite reaction force.

Remember:

Equal force

Opposite direction

Same time

NOT:

❌ Bigger mass = bigger force

The forces are ALWAYS equal.

The lighter object simply accelerates more.

Common Physics Exam Traps 🚨

Velocity

Always include direction.

3.2 km/h North ✅

3.2 km/h ❌

Displacement

Never add total distance.

Only:

finish - start

Third Law

Never say:

Heavier object exerts greater force ❌

Say:

Forces are equal and opposite.

F = ma comprehension questions

Always say:

Mass stays constant.

Acceleration changes.

Therefore force changes.

🧬 BIOLOGY

DNA

DNA = Deoxyribonucleic Acid

Functions:


  • carries genetic information


  • codes for proteins

Nucleotides

Building blocks of DNA.

Contains:


  • deoxyribose sugar


  • phosphate


  • nitrogenous base

Base Pairs

A ↔ T

C ↔ G

Remember:

Adenine ↔ Thymine

Cytosine ↔ Guanine

Gene

A section of DNA that:


  • codes for a specific trait

Chromosome

Tightly coiled DNA that:


  • contains many genes

DNA Replication

Purpose:


  • make identical copies of DNA before cell division

Occurs:


  • before mitosis and meiosis

Enzymes

Helicase


  • unzips DNA

DNA Polymerase


  • adds complementary nucleotides

DNA Ligase


  • seals the DNA backbone

Alleles

Different versions of the same gene.

You inherit:


  • one from each parent

Dominant vs Recessive

Dominant:


  • uppercase


  • shown if one is present

Recessive:


  • lowercase


  • shown only if both are recessive

Genotype vs Phenotype

Genotype

Allele combination.

Examples:

RR

Rr

rr

Phenotype

Physical trait.

Examples:

Red flower

White flower

Homozygous vs Heterozygous

Homozygous

Two same alleles.

RR

rr

Heterozygous

Two different alleles.

Rr

Pedigrees

Dominant or Recessive

Dominant


  • appears every generation

Recessive


  • can skip generations

Autosomal or X-linked

Autosomal


  • males and females affected similarly

X-linked


  • mostly males affected

Remember:

Father → daughters

Mother → sons

MITOSIS

Purpose:


  • growth


  • repair

Produces:


  • 2 identical daughter cells

Chromosomes:

2n → 2n

PMAT

Prophase

Chromosomes visible

Nucleus breaks down

Metaphase

Chromosomes line up

Anaphase

Sister chromatids separate

Telophase

New nuclei form

Then:

Cytokinesis

Cell splits.

MEIOSIS

Purpose:


  • produce gametes

Produces:


  • 4 non-identical cells

Chromosomes:

2n → n

Meiosis creates variation


  1. Crossing over


  2. Independent assortment

Haploid vs Diploid

Haploid (n)

Half chromosomes

Examples:

Sperm

Egg

Diploid (2n)

Full chromosomes

Examples:

Body cells

Natural Selection (THE 4 STEP CHAIN)

1⃣ Mutation

Mutations create variation.

↓

2⃣ Selection pressure

More offspring are produced than survive.

↓

3⃣ Survival of the fittest

Some traits are more favourable.

↓

4⃣ Future generations

Favourable traits are passed on.

Speciation

Definition:

The process where one species splits into two, responsible for the formation of new species.

3 steps:

Variation

Differences exist.

↓

Isolation

Populations separate.

↓

Selection

Different environments favour different traits.

↓

New species form.

Allopatric vs Sympatric

Allopatric

Different locations.

(Geographical isolation)

Sympatric

Same location.

(Reproductive isolation)