Physics (school) · Part 01
Motion and measurement
How to describe movement with numbers, units and graphs.
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- SI unitsThe standard units scientists share worldwide: metre (m) for length, kilogram (kg) for mass and second (s) for time.
- Scalar and vectorA scalar has size only, like 5 kg. A vector has size and direction, like 5 N to the left.
- SpeedHow far something travels each second. Speed = distance / time.
- VelocitySpeed in a stated direction. It is a vector, so changing direction changes velocity even if the speed stays the same.
- Distance-time graphA graph with time along the bottom and distance up the side. The slope (gradient) of the line is the speed.
- AccelerationHow quickly velocity changes. Acceleration = change in velocity / time, measured in m/s squared.
- Velocity-time graphA graph of velocity against time. The gradient is the acceleration. The area under the line is the distance travelled.
- Equations of uniform accelerationFor steady acceleration: v squared = u squared + 2as, where u is start velocity, v is end velocity, a is acceleration and s is distance.