# [Unlocked] Example Must Contain Substantive

[Unlocked] Example Must Contain Substantive

**You are driving a car down a straight highway when you come upon a sudden accident.****You slam on your brake to avoid hitting the car in front of you.****Describe any changes in the motion of your car in terms of velocity and acceleration.****Feel free to embellish your account of values of your own choosing.**

- In addition to defining the concepts, you must illustrate them by applying them to an example. Your example must contain substantive details.
- Support the information presented in your initial post with appropriate references.

There are two types of numeric quantities in physics: vectors and scalars. Understanding these two concepts allow you to more successfully describe and understand physical phenomena.

A scalar quantity is a magnitude that describes a measurement or amount. For example, the temperature is a scalar quantity. Temperature is a measurement of the relative hotness or coldness of an object and it doesn’t have a directional dependence. Speed is another example of a scalar quantity as a measurement of how fast an object is moving.

Velocity is a vector composed of both speed and direction (example: car moving 30 mph towards the East). In this course, we will not explore vector algebra. Instead, we will stick with a one-dimensional analysis where the direction is indicated by either (+) or (-). Acceleration is also a vector because it is defined as the time rate of change in velocity. Since velocity is speed and direction, that means acceleration can be a change in speed, a change in direction, or both changes in speed and direction relative to time.

Force is also a vector quantity. Newton’s second law defines force as the product of mass (a scalar) and acceleration (a vector) so the result is a force vector. By definition, a force causes objects to accelerate, so this means that when a force is applied the acceleration can be a change in speed, a change in direction, or a change in both speed and direction.

The acceleration due to gravity at the Earth’s surface is 9.8 m/s^2. It is a vector that points towards the center of the Earth. Weight is a force defined as the product of mass and acceleration due to gravity. That makes weight a vector as well.