Speed, average speed and acceleration
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The teaching part (1 min) is free to watch. A free account opens the whole lecture: 4 worked examples, 10 practice questions, 1 real past-paper question with the answer explained, the mistakes that lose marks, the full-marks tip, a one-card summary and a quick quiz.
What this lecture covers
- How fast, and how quickly?
- Speed
- One equation, three forms
Read the transcript of the teaching part
Last time
Before we start: last time, in Scalars, vectors and resultants, you learned these points. Here they are again on one card. Keep them in mind, because today builds on them.
How fast, and how quickly?
A sprinter explodes off the blocks, and a train glides into a station. Two ideas describe them. Speed tells us how fast something moves. Acceleration tells us how quickly its speed changes. Let us take them one at a time.
Speed
Speed is the distance travelled in each second. We find it by dividing the distance by the time. Distance is measured in metres, and time in seconds, so speed is in metres per second. A runner who covers one hundred and fifty metres in twenty seconds has a speed of seven point five metres per second. Speed has size only, so it is a scalar. Velocity is speed in a stated direction.
One equation, three forms
The same equation gives three answers. To find the speed, divide distance by time. To find the distance, multiply speed by time. To find the time, divide distance by speed. Write which one you want, then substitute.
How often it comes up
How often Cambridge has asked each part, counted by ExamYard from every past paper in its question bank: Acceleration and deceleration · Speed, velocity and average speed.
Chapter 1.2: Motion
- Speed, average speed and acceleration 6 min
- Distance–time graphs and drawing motion graphs 5 min
- Speed–time graphs: gradient and area 5 min
Also for O Level Physics 5054
Which topics come up most in O Level Physics 5054 past papers, counted from every paper since 2004.