# 1.2.1 Speed & Acceleration

### Speed

• Speed (measured in metres per second) is the distance moved by an object each second
• The average speed of an object is given by the equation: • You can rearrange the equation with the help of the formula triangle: #### Exam Tip

• Use the units of speed (metres per second – distance divided by time) to help you remember the formula
• The equation is for average speed, but the speed at a specific moment might be higher or lower
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### Velocity

• Velocity is a similar quantity to speed, but includes a direction (the direction of travel) as well as its value (its magnitude)
• Two objects can have equal speeds but might have opposite velocities (if they are travelling in opposite directions) The two cars have the same speed but opposite velocities, because they are travelling in opposite directions

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### Acceleration

• Acceleration is the rate of change of velocity: In other words, how much the velocity of an object changes by every second
• Acceleration is given by the equation: (Where u is the initial velocity of an object and v is its final velocity)

• You can rearrange this equation with the help of the formula triangle: • The units of acceleration are m/s2, which mean the same thing as m/s/s – the change in velocity (in m/s) every second

#### Exam Tip

Marks are often available for giving the correct unit, even if your answer is incorrect. You must, however, give an answer (even if it’s just a guess): giving a unit without an answer will not gain you any marks. ### Author: Jenna

Jenna studied at Cardiff University before training to become a science teacher at the University of Bath specialising in Biology (although she loves teaching all three sciences at GCSE level!). Teaching is her passion, and with 10 years experience teaching across a wide range of specifications – from GCSE and A Level Biology in the UK to IGCSE and IB Biology internationally – she knows what is required to pass those Biology exams.
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