EasyPhysicsHigh School (11–12)Mechanics › Vectors and Motion in a PlaneConceptualBoard ExamAPA-LevelIB
Sort these into scalars and vectors: distance, displacement, speed, velocity, mass, weight, energy…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Sort these into scalars and vectors: distance, displacement, speed, velocity, mass, weight, energy, temperature, acceleration, time, electric current.
One of them has a direction, but is still a scalar. Which one, and why?
Need a reminder? The key ideaShow
Ask two questions. Does it have a direction? Does it add like arrows, by the triangle rule? A vector passes both tests. A scalar fails at least one.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Plan. Use the two tests: a direction, and adding like arrows.
Step 1. The vectors. Displacement, velocity, weight and acceleration. Each has a direction and adds like arrows. Weight is a force that points straight down.
Step 2. The scalars. Distance, speed, mass, energy, temperature and time. Each has a size only.
Step 3. The odd one. Electric current flows one way along a wire, so it seems to have a direction. But two currents that meet at a junction add as plain numbers, whatever the angle between the wires. It fails the second test, so it is a scalar.
Answer: Vectors: displacement, velocity, weight, acceleration. Scalars: distance, speed, mass, energy, temperature, time and electric current. Electric current has a direction, but it is a scalar.
Watch out. Mass and weight are different. Mass, in kilograms, is a scalar. Weight, in newtons, is a force, so it is a vector.
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