Speed, Distance and Time
The speed of an object is the distance it travels per unit time
Speed is a scalar quantity.This is because it only contains a magnitude (without a direction)
For objects that are moving with a constant speed, use the equation below to calculate the speed:
Speed= distance travelled/ time taken
Where:
Speed is measured in metres per second (m/s)
Distance travelled is measured in metres (m)
Time taken is measured in seconds (s)
Instantaneous Speed: The speed of the object at any specific point in time is given by the height of the graph at that moment. For example, if you read the speed at a particular second, it gives you the instantaneous speed.
Average Speed
In some cases, the speed of a moving object is not constant
For example, the object might be moving faster or slower at certain moments in time (accelerating and decelerating)
The equation for calculating the average speed of an object is:
Average speed= total distance covered / total time taken
Let’s solve some examples;
Imagine a speedy snail named Speedy Sally 🐌 racing along a garden path. Sally covers a distance of 10 metres in 5 seconds. To calculate her speed, you can use the formula:
Speed (v) = Distance (s)Time (t)
So for Speedy Sally:
Speed = 10 m / 5 s
= 2 m/s
Speedy Sally is zooming at 2 metres per second!
VELOCITY
Now, let’s talk about velocity, which not only considers how fast you’re going but also the direction. Imagine you’re riding a cool scooter around the block. You travel 15 metres to the east in 3 seconds. Your velocity can be calculated using the formula:
Velocity (v) = Displacement (s)Time (t)
Where:
v = velocity in metres per second (m/s)
s = displacement, measured in metres (m)
t = time, measured in seconds (s)
Velocity is a vector quantity, so it uses displacement, s, rather than distance which is scalar. Since you’re going to the east, we consider east as the positive direction. So, for your scooter ride:
Velocity = 15 m (east) / 3 s
= 5 m/s (east)
Your velocity is 5 metres per second to the east.
