Unit 7 — Forces, Motion, Energy, Electricity, and Magnetism

Welcome back!

Physics helps us understand how the universe behaves.

From the motion of planets to the operation of smartphones, the laws of physics explain countless natural phenomena and modern technologies.

In this unit, you will investigate forces, motion, energy, electricity, magnetism, and waves.

Reviewing Newton's Laws

Sir Isaac Newton described three fundamental laws of motion.

First Law

Objects remain at rest or continue moving in a straight line unless acted upon by an unbalanced force.

Second Law

Greater force produces greater acceleration, while greater mass requires more force to produce the same acceleration.

The relationship is often written as:

Force = mass × acceleration

(F = ma)

Third Law

For every action, there is an equal and opposite reaction.

These laws describe motion throughout the universe.

Energy

Energy is the ability to perform work or produce change.

Common forms include:

• kinetic
• potential
• thermal
• electrical
• chemical
• nuclear
• light
• sound

Energy constantly changes from one form into another.

The total amount of energy remains constant according to the Law of Conservation of Energy.

Electricity

Electricity results from the movement of electric charge.

Electric circuits require:

• an energy source
• conducting materials
• a complete pathway

Common electrical components include:

• batteries
• wires
• switches
• resistors
• light bulbs
• motors

Modern civilization depends heavily upon electrical systems.

Magnetism

Magnets produce invisible magnetic fields.

Every magnet has:

• a north pole
• a south pole

Like poles repel.

Unlike poles attract.

Electricity and magnetism are closely connected.

Moving electric charges create magnetic fields.

Many technologies depend upon this relationship.

Electromagnets

An electromagnet forms when electric current flows through a wire, usually wrapped around an iron core.

Electromagnets are used in:

• electric motors
• generators
• speakers
• cranes
• medical equipment
• transportation systems

Unlike permanent magnets, electromagnets can be turned on and off.

Waves

A wave transfers energy from one place to another.

Major types include:

• sound waves
• light waves
• water waves
• seismic waves

Important wave properties include:

• wavelength
• frequency
• amplitude
• speed

Different types of waves behave differently while transferring energy.

Electromagnetic Waves

Light is one example of an electromagnetic wave.

The electromagnetic spectrum includes:

• radio waves
• microwaves
• infrared
• visible light
• ultraviolet
• X-rays
• gamma rays

These waves differ mainly in wavelength and frequency.

They have many important applications in communication, medicine, astronomy, and engineering.

Physics in Everyday Life

Physics explains many everyday technologies.

Examples include:

• automobiles
• bicycles
• elevators
• computers
• smartphones
• airplanes
• satellites
• renewable energy systems

Understanding physics helps engineers design safer and more efficient technologies.

Activity

Complete the following:

• identify examples of Newton's three laws
• classify forms of energy
• build or diagram a simple electric circuit
• investigate permanent magnets and electromagnets
• identify examples from the electromagnetic spectrum
• observe different types of waves

Explain your observations using scientific reasoning.

Practice

Answer these questions.

What are Newton's three laws of motion?

What is the Law of Conservation of Energy?

What is required for an electric circuit?

How are electricity and magnetism related?

What is an electromagnet?

What properties describe waves?

Review

Today you learned:

• Newton's laws explain motion
• energy exists in many forms and is conserved
• electricity depends on moving electric charges
• magnetism and electricity are closely connected
• electromagnets have many practical uses
• waves transfer energy
• electromagnetic waves make many modern technologies possible

Physics helps explain the natural laws that govern movement, energy, and technology throughout the universe.

Looking Ahead

Next we will explore Earth, the solar system, stars, galaxies, and the universe, learning how astronomy helps us understand our place in space.