Physics·General Physics · NSSCO 2.3.3
Acceleration & motion graphs
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Speed tells you how fast something moves; acceleration tells you how quickly that speed is CHANGING. In this lesson we define acceleration as the rate of change of velocity, a = (v − u) ÷ t, learn what positive and negative values (deceleration) mean, meet the acceleration of free fall g ≈ 10 m/s², and then read the two graphs the examiner loves — distance–time and speed–time. We'll see that the gradient of a distance–time graph is the speed, the gradient of a speed–time graph is the acceleration, and the area under a speed–time graph is the distance travelled.
What you'll learn in this lesson
By the end you should be able to (NSSCO Physics 2.3.3):
- Define acceleration as the rate of change of velocity, a = (v − u) ÷ t, measured in m/s²
- Explain what positive and negative values of acceleration mean (deceleration)
- Identify linear motion for which the acceleration is constant, and calculate the acceleration
- Identify motion for which the acceleration is not constant
- State that the acceleration of free fall near the Earth's surface is constant, about 10 m/s²
- Plot and interpret distance–time graphs, identifying rest, constant speed and changing speed, and find speed from the gradient
- Plot and interpret speed–time graphs, finding acceleration from the gradient
- Calculate the area under a speed–time graph to find the distance travelled for motion with constant acceleration
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