1. Thermal energy
   Kinetic energy
2. Electrical energy
   Light energy

One of the cornerstone concepts of physics is kinetic energy. The term is used to express the energy that an object in motion has. An object maintains kinetic energy until it changes speed.

1. Collision
   Displacement
2. Energy
   Force

A "force" refers to any interaction that will change the motion of something if left unopposed. It can alter an object from existing in a resting state to being in a state of motion.

1. An apple
   A shoe
2. A feather
   A rock

The notion that Sir Isaac Newton actually had the theory of gravity knocked into him by a falling fruit has been widely disputed, but it makes for a pretty incredible story about the origin of this theory. He published his famous work, "Principia," in 1687.

1. Solar flares
   Centrifugal force
2. The Earth's gravity
   The sun's gravity

The sun's gravity keeps all of the planets in our solar system locked into their orbits, circling the sun. It's a good thing, too, because, without it, our planet would veer off into outer space.

1. True
2. False

We use the word "friction" outside of the realm of physics, but scientifically it has a specific meaning. Kinetic friction refers to moving objects, and static friction refers to non-moving objects.

1. Absolute zero
   Displacement
2. Hubble’s Law
   Density

Displacement is a change in an object's location from its original position or a vector that covers the smallest distance between two points. It's determined by — what else — the displacement formula.

1. True
2. False

The middle of an atom is called the nucleus. The nucleus is made of subatomic particles — it's primarily comprised of protons and neutrons, with a very small number of electrons mixed in.

1. Watt
   Particle
2. Atom
   Ping

A "watt" is a standard unit used to measure power, equivalent to a single joule per second. A joule is a unit of energy. "Watt" is a common term, used to talk about electrical currents in our many devices.

1. Hydrostatic equilibrium
   Radioactive decay
2. Interference
   Wave function

Radioactive decay, also called nuclear decay, refers to the disintegration of an unstable nucleus. When radioactive decay happens, the atom emits radioactive energy, which is, of course, dangerous.

1. Protons
2. Electrons

Electrons are negatively charged particles, whereas protons are positively charged ones. All atoms contain the same number of protons and electrons, so they effectively cancel each other out.

1. A space that contains little or no matter and a very low pressure
   A space that is exactly the same, pressure-wise, as the air around it
2. A space that contains a ton of matter and very high pressure
   A space where only protons can exist

Most vacuums have no matter in them, and those that do have so little that it hardly even registers. They have very low pressure and are considered to be inhospitable environments.

1. Super energy
   Physics energy
2. Hot energy
   Atomic energy

Atomic energy is created through nuclear fission or nuclear decay. It is a powerful but sometimes unmanageable form of energy that can be dangerous if it is mishandled.

1. Wormhole
   Sonic boom
2. Supernova
   Redshift

A sonic boom is the loud noise that shock waves make when an object travels faster than the speed of sound. Chuck Yeager was the first pilot to break the sound barrier, back in 1947.

1. The change of the seasons
   Oceanic tides
2. Earthquakes
   Monsoons

Oceanic tides are primarily caused by the moon's gravity. For many years, these tides were considered one of the more mysterious phenomena on the planet, but now we understand why they happen.

1. Neptune
   Mars
2. Mercury
   Pluto

Back in 2006, Pluto was stripped of its planethood by scientists who decided that it just didn't meet all of the criteria — specifically, clearing its neighborhood of "other objects" near its size.

1. Light
   Sound
2. Orbit
   Solar

It's very hard to wrap your mind around the speed of light, which moves at an astonishing 186,282 miles per second. Light is by far the fastest-moving thing in our entire known universe.

1. The speed at which a meteor moves around the sun
   The tendency to preserve a state of rest or uniform motion unless acted upon by an external force
2. An object that orbits around a dwarf planet, like Pluto
   A formula designed to calculate the speed of sound

Who doesn't love a little guilty pleasure inertia once in a while? Anyone who has ever binged on Netflix knows that staying in a state of rest until forcibly moved is an underrated talent.

1. Concave
2. Convex

When an object rounds out like a sphere, it's considered to be convex. When light passes through a convex lens, it tends to bunch together rather than split apart on the other side.

1. Pascal
   Electronics
2. Gravity
   Mass

Gravity, in its simplest form, means that objects with mass tend to be attracted to each other. Since virtually everything on our planet has mass, we are firmly rooted to the Earth.

1. Albert Einstein
   Galileo Galilei
2. Stephen Hawking
   Isaac Newton

Let's talk about Albert Einstein's famous theory of relativity! This varsity level concept basically states that our perception of gravity is based on the curvature of space and time.

1. True
2. False

Actually, the opposite is true. The universe is expanding, and it seems to be expanding at a much higher rate than it has in the past. Don't worry — this doesn't have any real effect for us humans.

1. The way light looks when reflected through a prism
   A space/time principle that explains alternate universes
2. What happens when a sound wave meets a light wave
   A flow of electricity through a conductor

Current generally flows from positive points to negative points. This term refers to the way an electrical force flows through a conductor. Metal is an exceptionally good conductor.

1. Metal
   Water
2. Rubber
   Wood

Since electricity always prefers to travel through the path of least resistance, it tends to avoid messing with rubber. Rubber is highly resistant and can stop an electrical current.

1. Gravitas
   Celsius
2. Kelvin
   Fahrenheit

Fahrenheit, Celsius and Kelvin are all valid measurements of temperature. Kelvin is rarely used outside of scientific scenarios, but Fahrenheit and Celsius certainly are. Fahrenheit is generally used in the United States.

1. Thomas Edison
   Charles Darwin
2. Sir Isaac Newton
   Nicola Tesla

You can thank Sir Isaac Newton and fellow scientist Gottfried Wilhelm Leibniz for your killer hard 10th-grade calculus class — the two men came up with calculus independently. Newton's three laws of motion are the building blocks of physics — he came up with those on his own.

1. Compass
   Prism
2. Microscope
   Flask

For an object to qualify as a prism, it has to have a few specific qualities. The ends must be identical and have flat faces. Of course, it must be clear so that light can pass through it.

1. Dark matter
   Black holes
2. Antimatter
   Light

Antimatter might sound like a sci-fi term, but it's actually a useful component of medical imaging, specifically, Positron Emission Tomography (PET). Also, antimatter occurs in cosmic rays, and it's studied for its unique properties.

1. Acceleration
   Datum
2. Event horizon
   Seismology

Acceleration can mean a number of different things, even just increasing speed while driving a car. In physics, acceleration is the rate of change of velocity in a certain amount of time.

1. True
2. False

As tough as it is to fully grasp, it's entirely possible — and even very likely — that some of the stars we gaze at in the night sky are not there any longer, thanks to the speed at which light travels.

1. One where oxygen is breathed
   One where the moon orbits our Earth
2. One that revolves around the sun
   One where planets rotate on their axes

Heliocentric universes — including ours — revolve around a star or sun. The idea that we live in a heliocentric universe was first envisioned by Copernicus, but it didn't catch on for centuries.

1. Funnel
   Magnetism
2. Phase
   Impulse

The term "impulse" refers to a sudden change in momentum — either an increase or a decrease. This can occur when an object either moves from a state of inertia or has a change in momentum.

1. There is an equal and opposite reaction.
   All actions are based on facts.
2. Actions can be measured in impulses.
   Action only occurs on a macro level.

Sir Isaac Newton's third law of motion states that "For every action, there is an equal and opposite reaction." This is one of the governing laws of physics and holds true for everything.

1. Galileo Galilei
   Marie Curie
2. Stephen Hawking
   Max Planck

Stephen Hawking was one of the most brilliant physicists who ever lived. His books, specifically "A Brief History of Time," made physics accessible and understandable to nearly everyone.

1. True
2. False

The Milky Way, a spiral shaped galaxy, is our home. Specifically, our planet is located in the Orion Arm of the galaxy. The Milky Way disk measures as much as 120,000 light-years in diameter.

1. Mass
   Variable
2. Datum
   Burette

In physics, the term "mass" is simply the measure of how much matter is in something. The mass of an object doesn't change, even if external forces are acting upon the object.