Step 7 of 18 · Forces · SC4-FOR-01
Balanced and unbalanced forces
Add the arrows. Balanced: no change in motion. Unbalanced: it speeds up, slows down or turns.
Learn it
Use force diagrams to find the net force and predict how an object's motion changes
Idea 1 of 4
A force is a push or a pull
Forces are measured in newtons (N) and drawn as arrows: the length shows the size, the arrowhead shows the direction. Contact forces need touching (friction, push, air resistance); non-contact forces act across a gap (gravity, magnetism, static electricity).
Know it by heart
Say each one in your head, then tap to check.
Try it
Play — nothing here is marked
- Speed
- 0.0 m/s · 0 km/h
- Time
- 0.0 s
Unbalanced
Net force 700 N downwards, so it speeds up downwards.
Speed–time graph
Press Run to start plotting.A full-marks answer
A skydiver weighs 700 N. Just after jumping, air resistance on her is 200 N. Calculate the net force and describe her motion.
3 marksBuilt one line at a time — say the next line before you reveal it
- The forces act in opposite directions, so subtract: 700 − 200.(weight down, air resistance up)
Words to know
Tap a card to flip it
Step 7 · last bit
Ready? Prove it.
A round of ten. Score 8 or more and this step is done — then on to mass, weight and friction.