Every push and pull is a force. Today we will add and remove forces on a heavy box — and you will predict whether it moves, speeds up, or stops.
Before we start — think about pushing a heavy shopping trolley — what makes it speed up, slow down, or stop?
We draw every force as an arrow. The arrow points the way the force pushes or pulls, and a longer arrow means a stronger force.
Gravity always pulls down; the ground pushes up to hold the box. A push can move it sideways, but friction rubs back against any sliding.
Add up the arrows. If they cancel out, the forces are balanced and the motion does not change. If one side wins, there is a leftover net force — the forces are unbalanced and the motion changes.