Vector quantities

Physics · Vectors

Switch the view, then tap a part of the diagram

Both forces point right, so both are positive: (+5 N) + (+3 N) = +8 N. The resultant is 8 N to the right.

Force A is always 5 N and Force B is always 3 N. Switch the view: only the directions change, yet the resultant does not stay the same.

Physics · Vectors

Distance is how far you travel along the route: 100 m + 300 m + 100 m = 500 m. It is a size and nothing more.

One walk to the shop, described two ways. Switch the view and compare.

Physics · Vectors

Vector or not?

Does this quantity carry a direction as well as a size?

10 of 10 still to sort.

Place each card, then read why it belongs there.

Predict, then check

Here is the twist. Commit to an answer before you look.

A car drives all the way round a roundabout at a steady 10 m/s. The speedometer never moves. What happens to the car’s velocity?

What you need to know

• What makes a quantity a vector — and which quantities are vectors.
• How an arrow shows a vector, and how to combine two vectors along a line.
• Why moving round a circle at a steady speed still changes your velocity.

The big picture

A vector quantity has a size and a direction; a quantity with a size only is not a vector. Vectors are drawn as arrows — length for size, arrowhead for direction — and along a line they combine using a plus sign for one direction and a minus sign for the other. Because direction is part of velocity, turning at a steady speed still changes the velocity.

⚠ Watch out

Adding the sizes of two vectors that point in opposite directions. Opposite directions work against each other, so give one direction a minus sign before you add, and always say which way the answer points.

Memory hook

A vector tells you HOW MUCH and WHICH WAY. Lose the "which way" and you have lost half of it.

Check yourself

Without looking back: name three vector quantities, and find the resultant of a 12 N force to the right and a 5 N force to the left on the same object.