Explain the difference between scalar and vector quantities.

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ishpiro eNotes educator| Certified Educator

A scalar quantity is a quantity that can be represented by one number. For example, a mass of a block could be 2 kilograms. Or, temperature could be -5 degree Celsius.

A vector quantity is a quantity that needs to be represented by at least two numbers. For example, velocity is a quantity that helps describe the motion. It indicates how fastsomething moves and in what direction. Another example of a vector quantity is force. Force, by definition, is a push or pull: to know the force, we need to know how hard the push or pull is and where it is directed. Other examples of vector quantities include acceleration, torque, and electric field.

Typically, a vector quantity is represented by magnitude and direction, usually given as an angle. Alternatively, it can be represented by the projections on the coordinate axis. In two dimensions, such as when an object is moving on a plane, the velocity vector `vecv` can be given by its components along x- and y- axes: `(v_x, v_y)` (Please see the reference link to read how these components describe the vector.) In a more general example of motion in three dimensions, you would need three numbers to describe the velocity `vecv` : its components along x-, y- and z-axes, `(v_x, v_y, v_z)` .




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