Final answer:
A scalar, such as temperature or speed, only has magnitude, while a vector, like displacement or velocity, includes both magnitude and direction. Scalars are measured merely by size while vectors are directional entities represented by arrows.
Step-by-step explanation:
In the study of motion and forces, it is essential to distinguish between scalar and vector quantities. Scalar quantities are defined by only magnitude, which is a measure of size or amount, without any direction. Examples of scalar quantities include temperature, such as 20°C, which simply specifies the intensity of heat, or speed, like 90 km/h, which indicates how fast an object is moving without regards to its directional path.
On the other hand, vector quantities are characterized by both magnitude and direction. This is important in scenarios where the direction is crucial to fully describe the physical situation. An example of a vector quantity is displacement, which indicates not only how far an object has moved but also the specific direction of that movement. Vectors are often represented using arrows to visually indicate their magnitude and direction.
For example, velocity is a vector because it describes an object's speed and the direction of its motion, such as a car traveling east at 100 km/h. This contrasts with speed, which would only provide the rate of travel (100 km/h) without the eastward direction—which is why speed is a scalar.
And for another scalar example, time is always just a magnitude, without a directional component. Understanding these differences is crucial in physics for accurately describing and predicting physical phenomena.