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P5 A) Scalar & Vector Quantities
P5 A) Scalar & Vector Quantities
There are two different types of quantities in science; these are scalar and vector quantities.
A vector quantity has both magnitude (size) and direction. For example, velocity is a vector quantity, and an example of a velocity is 5 metres per second (m/s) in a northwards direction. This is a vector quantity because it has both magnitude (5 m/s) and direction (a northwards direction).
A scalar quantity only has magnitude; it has no direction. An example of a scalar quantity is speed, such as an object travelling at a speed of 40 miles per hour (mph). 40 mph has a magnitude, but there is no direction; we do not know if the object is travelling in a northwards direction, eastwards direction or constantly changing direction (such as going round in circles).
You will come across many different scalar and vector quantities during the whole science GCSE course.
A vector quantity has both magnitude (size) and direction. For example, velocity is a vector quantity, and an example of a velocity is 5 metres per second (m/s) in a northwards direction. This is a vector quantity because it has both magnitude (5 m/s) and direction (a northwards direction).
A scalar quantity only has magnitude; it has no direction. An example of a scalar quantity is speed, such as an object travelling at a speed of 40 miles per hour (mph). 40 mph has a magnitude, but there is no direction; we do not know if the object is travelling in a northwards direction, eastwards direction or constantly changing direction (such as going round in circles).
You will come across many different scalar and vector quantities during the whole science GCSE course.
Vector quantities have both magnitude and direction. Here are some examples of vector quantities.
> Velocity – 5 m/s north
> Force – 80 N left
> Displacement – 10 kilometres east
> Weight – 300 N down
> Acceleration – 3 metres per second squared (m/s2) to the right
> Momentum – 80 kilogram metres per second (kg m/s) west
Scalar quantities just have magnitude (they do not have direction). Here are some examples of scalar quantities.
> Speed – 40 miles per hour (mph)
> Distance – 23 metres
> Energy – 6,500 joules
> Mass – 10 kilograms
> Temperature – 29°C
> Density – 2.9 g/cm3
Vector Diagrams
We usually represent vector quantities by drawing arrows. Vector quantities have both magnitude (size) and direction. The length of the arrow is the magnitude of the vector, and the direction of the arrow is the direction of the vector. Here is an example of some of the forces acting on a car.
We usually represent vector quantities by drawing arrows. Vector quantities have both magnitude (size) and direction. The length of the arrow is the magnitude of the vector, and the direction of the arrow is the direction of the vector. Here is an example of some of the forces acting on a car.
We can see from the above diagram that the arrow for the driving force is longer than the arrows for air resistance and friction; this tells us that the driving force is larger (has a greater magnitude) than air resistance and friction. Also, from the above diagram, we can see that the driving force is acting towards the right and both air resistance & friction are acting towards the left.