Every push and pull is a force. You usually can't see them — but for the next few minutes, you can.
Start hereEvery time something starts moving, speeds up, slows down, stops, or turns a corner, a force made it happen. Nothing changes its motion on its own.
A force is a push or a pull — that's the whole definition. Scientists measure how strong a force is in a unit called the newton (N). Holding a small apple in your hand takes about one newton of push from your palm. Picture every force as an arrow: the way it points is the direction of the push, and the longer the arrow, the stronger the pull.
Here's the tricky part. You might think forces only show up when things zoom around. But forces are working constantly, even on things sitting perfectly still.
Look at a book resting on a table. It's not going anywhere — yet two forces are locked in a tug-of-war right now. Gravity pulls the book straight down toward the floor. At the same time, the table pushes straight up on the book with exactly the same strength. The two arrows cancel, so the book stays put. Take the table away, and gravity wins instantly.
Gravity pulls down; the table pushes up. Equal arrows, no movement.
Magnetism pulls in; gravity pulls down. It clings without touching.
Gravity holds you in your chair while the seat pushes back up.
Earth's gravity keeps pulling it, curving its path into a circle.
The big surprise: "not moving" doesn't mean "no forces." It usually means the forces are perfectly balanced, quietly cancelling each other out.
Drag from the box to fling out a force arrow — the direction you drag is the way you push, and the farther you drag, the stronger the push. Watch the box start, speed up, slow, stop, or turn. No mouse? Use the buttons and slider below.
Give the box a push and see which way the net arrow points.
When you add up all the arrows on an object, you get one single arrow called the net force. This is the master rule of the whole topic:
Notice what balanced does not mean: it doesn't only mean "stopped." A hot-air balloon drifting at a steady, gentle speed also has balanced forces — the push forward and the drag backward are equal, so nothing changes. Motion changes only when the arrows stop being equal.
Imagine two teams pulling a light basket that hangs under a balloon, floating so gently it barely resists.
Try this in the lab above: push the box right, then push it left with the same strength. The two arrows cancel and the box coasts — you just built balanced forces with your own hands.
Two ropes pull the ring in opposite directions. Change how hard each side pulls and watch the leftover arrow — the net force — shrink or grow. Can you make it perfectly balanced?
Equal pulls make a net force of zero — the ring holds perfectly still.
Every effect a force has fits into one of five simple changes. As you read, picture the arrow that causes each one:
A still soccer ball won't move until your foot pushes it.
Keep pedalling and the bike goes faster — the push keeps adding.
Squeeze the brakes and friction pushes back until you crawl.
A wall pushes back so hard a rolling ball halts at once.
A steady sideways pull — like the string on a swinging conker, or gravity on the Moon — bends a straight path into a curve. The object never speeds up or slows, it just keeps changing direction.
One quick question. Read it, pick an answer, and see if your arrows line up.
The trap is thinking that moving means a force is pushing. Once something is already gliding, it keeps gliding on its own. A force is only needed to change that motion — to start, speed, slow, stop, or turn it.
A force is a push or a pull, measured in newtons — draw it as an arrow.
All the arrows combine into one net force. Balanced arrows cancel to zero.
Only an unbalanced net force starts, speeds, slows, stops, or turns things.