The first video related to this weeks material introduces the mathematical concepts of vectors and scalars and their importance to mechanics and analyzing physical situations. In brief, a scalar is a description of the magnitude of something but the magnitude is the only piece of information that is being communicated. For example, Speed, is a scalar quantity and if we were to say that a car had a speed of 20 m/s (meters per second) that is all we would know about the car. We would not know which direction it is travelling. A vector quantity, is a quantity that has both a magnitude and a direction associated with it. So when we say that the velocity of a car is <20,0,0> m/s then we know that it is moving at 20 m/s in the positive x-direction. The positive x direction because the the 20 is in the first space of the vector <x,y,z> and there is no negative sign. Positive x might not mean anything to you in regards to understanding the direction unless you map a x, y plane onto the cardinal directions. Where +x is East, -x is West, +y is North and -y is South.
In the next pre-class video we examine the ideas of velocity and displacement, which are two vector quantities. We discuss what they mean and how they relate to their scalar related quantities and their application to solving mechanics based problems.
The final video discusses relative velocity. This video highlights that although we conceive of velocities in our every day life we often do not think about the importance of how they are observed. In simple terms the velocity of a bus is relative to who is observing the bus. If the person observing bus is stationary, the bus will have a different velocity to the person than if the person was walking. We often do not consider this in our daily life. The relative nature of a velocity might not be considered in a physics problem if all velocities given are relative to the same observation point. However, if different observation points are being used then we need to understand how the velocities relate to each other and there observation points.
Trinity Walton Club Activity Archive 