Edexcel A Level Physics:复习笔记2.4 Scalars & Vectors

• A scalar is a quantity which only has a magnitude (size)
• A vector is a quantity which has both a magnitude and a direction
• For example, if a person goes on a hike in the woods to a location which is a couple of miles from their starting point
  • As the crow flies, their displacement will only be a few miles but the distance they walked will be much longer

   

Displacement is a vector while distance is a scalar quantity

• Distance is a scalar quantity because it describes how an object has travelled overall, but not the direction it has travelled in
• Displacement is a vector quantity because it describes how far an object is from where it started and in what direction
• Some common scalar and vector quantities are shown in the table below:

Scalars and Vectors Table

Vector Notation

The arrow on vector notation does not indicate an actual direction, just that the quantity has a direction

• This means writing the quantity to make it clear that it is a vector
• In text books vectors are often shown as bold and italic, for example F or s
• Another form of notation, and easier to do in handwriting, is putting an arrow over the top of the quantity, for example or
  • The arrow does not indicate the actual direction of the vector, only that is has a direction