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What is acceleration? | Page 1 Here is what ‘acceleration’ means in physical science: In other words, acceleration is how much an object changes its velocity in a certain period of time. Velocity is a measure of both speed and direction. If you change either speed or direction, you change velocity. That means that acceleration is a measure of how much an object changes its speed (by going either faster or slower) or its direction or both during a certain amount of time. Formulaically, it can be written as: In this equation:
- (a) is acceleration,
- (v) is velocity,
- (t) is time, and
- the delta symbol (Δ) means ‘change in’. In other words, this equation says that acceleration (a) is the change in velocity (Δv) over the change in time (Δt).
What is acceleration?
WOW sheet
Document number: 3.2.3.8.5.1 Rev.1. Acceleration is the change in the velocity of an object over the change in time. a = Δv/Δt
Acceleration is NOT the same as ‘going fast’ Outside of physical science, the term ‘accelerate’ is sometimes used to mean ‘go fast’. In physical science, however, that’s not what ‘acceleration’ means. For something to be accelerating, there needs to be a change happening to how that object is moving. In other words, there needs to be a change to its velocity. Either the speed needs to be changing (faster or slower), the direction needs to be changing, or both. If nothing is changing, then the object is not accelerating, no matter how fast it might be moving! Have you ever been in a train or a plane that was traveling along really smoothly? If the ride was smooth enough and you closed your eyes, you probably wouldn’t even be able to tell you were moving and not just sitting still. But when the vehicle changes velocity, you can definitely tell you are moving. Think about what it feels like when the train slows down as it approaches a stop or the plane 👁🗨 Here’s an example In a car, you can accelerate by hitting the gas (increasing speed) or by hitting the break (decreasing the speed) or by turning the steering wheel (changing direction). If you are just coasting in a straight line at a constant speed, no matter how fast, you aren’t accelerating. You are moving, of course, but being in motion is different to accelerating.
Unit of measure The unit that acceleration ( a ) is measured in is meters per second squared ( 𝑚 𝑠^2
Remember that acceleration is measuring the change in velocity over the change in time. You can think about the unit of measure as explaining the change in velocity, which is ‘meters per second’ over the change in time, which is ‘per second’. In other words, ‘meters per second per second.’ It’s just easier to say ‘meters per second squared’. Calculating acceleration To calculate acceleration, you need to use the formula: a = Δv/Δt To find the change in velocity, subtract the starting velocity from the end velocity. To find the change in time, subtract the starting time from the end time. You then divide the change in velocity by the change in time. That gives you your answer.
Example: the snail’s sports car
For this example, we will calculate the acceleration for a sports car owned by a snail.
Have you ever noticed that speedometers are written as ‘distance per time’? It’s true! A car’s speedometer shows how many kilometres per hour it is traveling (or maybe how many miles per hour). If a police officer says you were going 100 kilometres per hour, that means that your speed was such that you could travel 100 kilometres in 1 hour. You can write that as 100 𝑘𝑚 ℎ𝑟 (which you may have seen written as 100 km/hr). Our snail’s car has a speedometer that shows metres per second. The snail’s car is on a straight road, pointing east. To start, the snail’s car isn’t moving. It has a speed of zero metres per second, which we can write as 0 𝑚 𝑠
The snail pushes down the gas pedal and the car starts to go! After five seconds, the car’s speedometer shows 10 𝑚 𝑠
What’s the snail’s acceleration?
The maths
The formula for calculating acceleration is: a = Δv/Δt First, let’s find the change in the snail’s velocity. To find the change in velocity, we subtract the starting velocity from the end velocity: Δv = ( 𝑚 𝑠
𝑚 𝑠
To find the change in time, we subtract the starting time from the end time: Δt = ( 5 s – 0 s)
