Science - Grade 6
Energy, Simple Machines, Electricity, and the Solar System
Table of Contents
1. Forms of Energy
Energy is the ability to do work or cause change. It exists in many forms and can be transferred from one object to another. Energy cannot be created or destroyed, only transformed.
Kinetic Energy (Energy of Motion)
Energy that an object has because it is moving.
Examples: Running water, moving car, swinging pendulum, wind
Formula: KE = Β½ Γ mass Γ velocityΒ²
Potential Energy (Stored Energy)
Energy stored in an object due to its position or condition.
Gravitational PE
Energy from height (book on shelf, water in dam)
Elastic PE
Energy from stretching/compressing (rubber band, spring)
| Form of Energy | Description | Examples |
|---|---|---|
| Mechanical | Energy of moving objects | Hammer, bicycle, wind |
| Thermal (Heat) | Energy from moving particles | Fire, hot water, sun |
| Chemical | Energy stored in bonds | Food, fuel, batteries |
| Electrical | Energy from electrons moving | Lightning, outlets, batteries |
| Light (Radiant) | Energy that travels in waves | Sunlight, lamp, screen |
| Sound | Energy from vibrations | Music, voice, thunder |
| Nuclear | Energy from atom's nucleus | Power plants, sun's core |
2. Energy Transformations
Energy transformation (or energy conversion) occurs when energy changes from one form to another. This happens constantly in our daily lives and in nature.
Law of Conservation of Energy:
Energy cannot be created or destroyed - only transformed from one form to another.
Common Energy Transformations:
Light Bulb:
Electrical Energy β Light Energy + Heat Energy
Car Engine:
Chemical Energy (fuel) β Mechanical Energy + Heat Energy
Electric Fan:
Electrical Energy β Mechanical Energy (rotation) + Sound Energy
Photosynthesis:
Light Energy β Chemical Energy (glucose)
Solar Panel:
Light Energy β Electrical Energy
Human Body:
Chemical Energy (food) β Mechanical + Heat + Electrical (nerves)
Note: In most transformations, some energy is "lost" as heat energy. This doesn't mean the energy disappears - it just becomes less useful for doing work.
3. Simple Machines
Simple machines are devices that make work easier by changing the amount, direction, or distance of force. There are six types of simple machines.
1. Lever
A rigid bar that rotates around a fixed point (fulcrum).
1st Class
Fulcrum in middle (seesaw, scissors)
2nd Class
Load in middle (wheelbarrow, nutcracker)
3rd Class
Effort in middle (broom, fishing rod)
2. Wheel and Axle
A wheel attached to a smaller axle; when one turns, so does the other.
Examples: Doorknob, steering wheel, screwdriver, ferris wheel
3. Pulley
A wheel with a groove for a rope; changes direction of force.
Fixed Pulley
Changes direction only (flag pole)
Movable Pulley
Reduces effort needed (crane)
4. Inclined Plane
A flat surface tilted at an angle (ramp).
Examples: Ramp, slide, wheelchair ramp, stairs
Benefit: Less force needed over longer distance
5. Wedge
Two inclined planes joined together; used to split or push apart.
Examples: Axe, knife, nail, chisel, plow, teeth
6. Screw
An inclined plane wrapped around a cylinder.
Examples: Screw, bolt, jar lid, spiral staircase, drill bit
4. Mechanical Advantage
Mechanical advantage (MA) measures how much a simple machine multiplies your effort force. It tells you how much easier the machine makes your work.
Basic Formula:
MA = Output Force Γ· Input Force
or
MA = Input Distance Γ· Output Distance
Lever:
MA = Effort Arm Γ· Load Arm
Longer effort arm = more mechanical advantage
Inclined Plane:
MA = Length of Ramp Γ· Height
Longer, gentler slope = more mechanical advantage
Pulley System:
MA = Number of supporting ropes
More pulleys = greater mechanical advantage
Example Problem:
A lever has an effort arm of 2 meters and load arm of 0.5 meters.
MA = 2 Γ· 0.5 = 4
This means the lever multiplies your force by 4!
5. Electricity Basics
Electricity is a form of energy caused by the movement of electrons (tiny particles with negative charge) through a conductor like wire.
Key Concepts:
Electric Charge
Positive (+) and Negative (-)
Opposite charges attract; like charges repel
Electric Current
Flow of electrons through a conductor
Measured in Amperes (A)
Voltage
Electric pressure that pushes current
Measured in Volts (V)
Resistance
Opposition to current flow
Measured in Ohms (Ξ©)
Types of Materials:
Conductors
Allow electricity to flow easily
Copper, aluminum, gold, water
Insulators
Block electricity flow
Rubber, plastic, glass, wood
Semiconductors
Can conduct under certain conditions
Silicon, germanium (used in computers)
Static vs. Current Electricity:
Static Electricity
Charges that stay in one place
Examples: Rubbing balloon on hair, lightning
Current Electricity
Charges that flow continuously
Examples: Electricity in homes, batteries
6. Electrical Circuits
An electrical circuit is a closed path through which electricity can flow. It needs a power source, conductors, and a load (device that uses electricity).
Parts of a Circuit:
Power Source
Battery or outlet - provides energy
Conductor (Wire)
Path for electricity to flow
Load
Device that uses power (light, motor)
Switch
Opens/closes circuit
Series Circuit
- * One path for current
- * All components connected in a line
- * If one bulb burns out, all go out
- * Same current through all
Parallel Circuit
- * Multiple paths for current
- * Components on separate branches
- * If one bulb burns out, others stay on
- * Same voltage across all
Ohm's Law:
V = I Γ R
Voltage (V) = Current (I) Γ Resistance (R)
Electrical Safety:
- * Never touch electrical appliances with wet hands
- * Don't overload outlets
- * Use circuit breakers and fuses
- * Stay away from downed power lines
7. The Solar System
The solar system consists of the Sun and all objects that orbit around it, including eight planets, dwarf planets, moons, asteroids, and comets.
The Sun:
- * A medium-sized star at the center of our solar system
- * Made mostly of hydrogen and helium
- * Produces energy through nuclear fusion
- * 109 times the diameter of Earth
- * Contains 99.8% of solar system's mass
The Planets (in order from Sun):
Memory tip: "My Very Eager Mother Just Served Us Nachos"
| # | Planet | Type | Key Features |
|---|---|---|---|
| 1 | Mercury | Terrestrial | Smallest, closest to Sun, no moons |
| 2 | Venus | Terrestrial | Hottest planet, rotates backward |
| 3 | Earth | Terrestrial | Has life, water, 1 moon |
| 4 | Mars | Terrestrial | Red planet, 2 moons, largest volcano |
| 5 | Jupiter | Gas Giant | Largest, Great Red Spot, 95+ moons |
| 6 | Saturn | Gas Giant | Famous rings, 146+ moons |
| 7 | Uranus | Ice Giant | Tilted on side, 27 moons |
| 8 | Neptune | Ice Giant | Windiest planet, 16 moons |
Other Solar System Objects:
Dwarf Planets
Pluto, Eris, Ceres, Makemake, Haumea
Asteroids
Rocky objects, mostly between Mars & Jupiter
Comets
Ice and dust, develop tails near Sun
Moons
Natural satellites orbiting planets
8. Earth in Space
Earth's position and movements in space cause many phenomena we experience, including day and night, seasons, and tides.
Earth's Movements:
Rotation
Spinning on its axis
Takes 24 hours (1 day)
Causes: Day and night
Revolution
Orbiting around the Sun
Takes 365.25 days (1 year)
Causes: Seasons (with tilt)
Seasons:
Caused by Earth's 23.5Β° tilt on its axis as it orbits the Sun.
Summer
Hemisphere tilted toward Sun (more direct sunlight)
Winter
Hemisphere tilted away from Sun (less direct sunlight)
Note: Philippines is near the equator, so we have less pronounced seasons (wet/dry instead).
Moon Phases:
The Moon orbits Earth in about 29.5 days, creating different phases.
π
New Moon
π
Waxing Crescent
π
First Quarter
π
Waxing Gibbous
π
Full Moon
π
Waning Gibbous
π
Last Quarter
π
Waning Crescent
Eclipses:
Solar Eclipse
Moon blocks Sun's light from reaching Earth
Occurs during New Moon
Lunar Eclipse
Earth blocks Sun's light from reaching Moon
Occurs during Full Moon
Key Takeaways
Energy
- * Forms: kinetic, potential, thermal, chemical, electrical, light, sound, nuclear
- * Energy transforms but never destroyed
Simple Machines
- * 6 types: lever, wheel & axle, pulley, inclined plane, wedge, screw
- * MA = Output Force Γ· Input Force
Electricity
- * Current, Voltage, Resistance
- * Ohm's Law: V = I Γ R
- * Series vs. Parallel circuits
Solar System
- * 8 planets: Mercury to Neptune
- * Rotation = day/night
- * Revolution + tilt = seasons