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Physics vocabulary · Motion and Forces

Speed

Meaning in physics, with examples

/spiːd/nounCore term

In physics, speed means: How fast an object is moving, found by dividing the distance travelled by the time taken. It has no direction, so it is a scalar, measured in metres per second (m/s).

In Turkish: sürat, hız

How it is used

Used for average speed, instantaneous speed and constant speed. A speedometer shows speed, not velocity. Exam questions often contrast the two: a car going round a bend at constant speed is still accelerating, because the direction of its velocity changes.

Example sentences

  1. Her average speed over the 400 m race was 8 m/s.

  2. The speed of sound in air is about 340 m/s at room temperature.

Common collocations

  • average speed
  • constant speed
  • top speed
  • speed of light
  • speed of sound
  • velocityHow fast an object moves in a particular direction. It is speed with a direction, so it is a vector, measured in metres per second (m/s).
  • displacementThe straight-line distance from an object's starting point to its final position, together with its direction. It is a vector, measured in metres.
  • scalarA quantity that has size (magnitude) but no direction, such as mass, time, temperature, energy or speed. Scalars are added like ordinary numbers.
  • accelerationThe rate at which an object's velocity changes over time. It can mean speeding up, slowing down or changing direction, and it is measured in metres per second squared (m/s²).
  • terminal velocityThe constant top speed reached by a falling object when the air resistance on it becomes equal to its weight, so the net force on it is zero.

More terms: Motion and Forces

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