Vectors and Scalars Quiz

Scalar quantities and vector quantities measure different aspects of the world, including forces as well as less tangible aspects such as energy and time. Scalars only have one part which is the magnitude or put simply amount.

Mass is a scalar quantity that measures the amount of matter in a certain volume or how many atoms there are. Weight on the other hand is a vector quantity. Vector quantities measure two things, the magnitude (amount) as well as the direction that the quantity is acting towards. To continue with the example of weight, it is a force that acts in a certain direction i.e. towards the centre of the Earth and is based on how much mass an object has.

Momentum is a vector quantity because it takes into account both mass and velocity. Objects have momentum when they are in motion and motion is always in a certain direction. Even spinning in place is a form of motion with constantly changing directions. Acceleration is another vector quantity that takes into account a magnitude as well as a direction. An object which is accelerating in a certain direction will gain a certain amount of velocity, which is itself a vector quantity being composed of speed and direction. 

Understanding the difference between scalar and vector quantities can help us to visualise what is happening in the world and make sense of motion, forces and energy. This is just one of the many tools of physics which we use to examine objects and make links between concepts. Newton’s Laws were an attempt to aid our understanding of motion and forces, an attempt that was extremely successful and we still learn about them today which is remarkable since they were first published in 1687.

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Moment of inertia is actually a tensor quantity, this means it sometimes behaves as a scalar and sometimes as a vector. Moment of inertia describes resistance to changing the rotational movement of an object, whereas inertia describes resistance to changing the state of motion. 

Inertia in a linear path is therefore a scalar quantity as it does not consider direction.