OpenStem

@openstem · Joined Jul 2026

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Flashcards7 cards

Why are soap bubbles always round?1 / 7

The thin soap film pulls itself into the smallest possible shape it can hold, and a sphere (a round ball shape) is the smallest shape that can hold air inside.

Physics

Physics · L1 · Bubbles & Surface Tension

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Flashcards7 cards

What is friction?1 / 7

Friction is a rubbing force between two surfaces that touch each other. It slows down or stops things that are sliding.

Physics

Physics · L1 · Friction: Why Things Slow Down

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Flashcards7 cards

What is a heat conductor?1 / 7

A material that lets heat move through it easily, like metal. Heat conductors feel cold to the touch because they carry heat away from your warm hand quickly.

Physics

Physics · L1 · Keeping Warm: Insulators & Conductors of Heat

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Flashcards7 cards

What is a light source?1 / 7

A light source is something that makes its own light, like the sun, a candle flame, or a glowing lightbulb.

Physics

Physics · L1 · Where Light Comes From: Sources vs Reflections

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Flashcards7 cards

What is a pendulum?1 / 7

A pendulum is anything that hangs from a point and can swing freely back and forth, like a playground swing or a clock's swinging weight.

Physics

Physics · L1 · Swings & Pendulums: Back-and-Forth Motion

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Flashcards7 cards

What happens if you rub a balloon on your hair?1 / 7

The balloon picks up a tiny electric charge, and your hair picks up the opposite charge — so your hair gets pulled toward the balloon and stands up.

Physics

Physics · L1 · Static Electricity: Balloons & Hair

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Flashcards7 cards

What is wind?1 / 7

Wind is air that is moving. You can't see the air itself, but you can feel and see what it pushes.

Physics

Physics · L1 · Wind & Moving Air: Kites, Sails & Pinwheels

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Flashcards8 cards

What shape is the glass in a magnifying glass?1 / 8

It's thicker in the middle and thinner at the edges — curved outward on both sides, like a tiny dome.

Physics

Physics · L1 · Magnifying Glasses & Simple Lenses

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Flashcards6 cards

What is speed?1 / 6

Speed is how far something moves in a certain time. Speed = distance ÷ time.

Physics

Physics · L2 · Speed: Distance and Time

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Flashcards5 cards

What is energy?1 / 5

Energy is the ability to do work or cause change. Without energy, nothing can move, grow, or change.

Physics

Physics · L2 · Energy Forms

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Flashcards9 cards

What does Newton's First Law say?1 / 9

An object at rest stays at rest, and an object in motion keeps moving at the same speed and direction, unless a force acts on it.

Physics

Physics · L2 · Newton's Three Laws

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A passenger lurches forward when a bus suddenly stops. Which law explains this?1 / 7

The First Law. The passenger's body was moving with the bus and tends to keep moving forward, even though the bus itself has stopped.

Physics

Physics · L2 · Newton's Three Laws

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Flashcards8 cards

What is an electric circuit?1 / 8

A complete loop that electricity can flow around, from a power source (like a battery), through wires and components, and back again.

Physics

Physics · L2 · Series Circuits

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Flashcards8 cards

What makes a circuit a parallel circuit?1 / 8

The components are connected on separate branches, side by side, giving electricity more than one path to choose from.

Physics

Physics · L2 · Parallel Circuits

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What is refraction?1 / 10

Refraction is the bending of light when it passes from one see-through material into another, like from air into water.

Physics

Physics · L2 · Refraction & Lenses

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Flashcards8 cards

What are the three ways heat can travel from one place to another?1 / 8

Conduction, convection, and radiation. Each one moves heat in a different way.

Physics

Physics · L2 · Heat Transfer

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A metal spoon left in a hot pot of soup becomes hot to the touch. Which mechanism?1 / 7

Conduction — heat travels particle to particle along the metal of the spoon.

Physics

Physics · L2 · Heat Transfer in Everyday Life

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Flashcards8 cards

What is density?1 / 8

Density is how much mass is packed into a given volume. Density = mass ÷ volume.

Physics

Physics · L2 · What Is Density?

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Flashcards9 cards

What is buoyant force?1 / 9

Buoyant force is the upward push a fluid (like water or air) gives to an object placed in it.

Physics

Physics · L2 · Buoyancy & Archimedes' Principle

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Flashcards9 cards

What is pressure, in simple terms?1 / 9

Pressure is how much force is pushing on a certain area. The same push can create more or less pressure depending on how spread out it is.

Physics

Physics · L2 · Pressure

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Flashcards10 cards

What are the two ends of a magnet called?1 / 10

The north pole and the south pole. Every magnet has both — you cannot have just one.

Physics

Physics · L2 · Magnetism & Electromagnets

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Flashcards8 cards

What does "work" mean in physics?1 / 8

Work is done when a force makes something move in the direction of the force. Pushing without any movement is not work in physics, even if it tires you out.

Physics

Physics · L2 · Work & Power

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Two climbers each climb the same 10 m staircase. Climber A takes 20 seconds, Climber B takes 40 seconds. Who does more work?1 / 7

Neither — they do the same amount of work, because they lift the same weight up the same height. Work does not depend on time.

Physics

Physics · L2 · Work & Power: Practice Problems

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Flashcards8 cards

What is momentum, in everyday words?1 / 8

Momentum is how hard something is to stop once it's moving. A moving object with a lot of momentum is hard to bring to a halt.

Physics

Physics · L2 · Momentum & Collisions

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Flashcards7 cards

Why does a crash at high speed feel far more dangerous than a crash at low speed?1 / 7

A faster-moving car has much more momentum, so far more motion has to be stopped very suddenly — that's what causes serious injury.

Physics

Physics · L2 · Momentum & Collisions

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Flashcards8 cards

What is static electricity?1 / 8

Static electricity is a buildup of electric charge sitting on the surface of an object, instead of flowing through a wire like electric current does.

Physics

Physics · L2 · Static Electricity

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Flashcards11 cards

What pushes electric current around a circuit?1 / 11

Voltage. Voltage is the electrical push that makes current flow through a circuit.

Physics

Physics · L2 · Introducing Ohm's Law

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What makes a magnet a 'permanent' magnet?1 / 10

A permanent magnet, like a bar magnet, is magnetic all on its own — no electricity needed. It keeps its magnetic pull all the time, unlike an electromagnet that only works when current flows through it.

Physics

Physics · L2 · Permanent Magnets & Field Lines

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Flashcards10 cards

What is friction?1 / 10

Friction is a force that resists motion between two surfaces touching each other. It always acts opposite to the direction something is sliding, or trying to slide.

Physics

Physics · L2 · Friction

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Flashcards10 cards

What does a wave carry from one place to another?1 / 10

Energy. A wave carries energy from place to place without carrying the matter it travels through along with it — the water, air, or rope stays roughly where it started.

Physics

Physics · L2 · Wave Basics

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