Physics Basics

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Key Questions

The following key questions are answered in this module:

What is speed and how does it work?
An object's speed is the distance that it moves in a measured time. Speed is a scalar quantity and is properly defined as the rate of change of position, which means the distance traveled per unit of time. Speed can be calculated using a simple formula and given in miles per hour (mph), in kilometers per hour (kph), or in the standard scientific measurement of meters per second (m/s).

How is velocity different from speed?
Velocity is dependent on the direction of motion. It has direction and is known as a vector quantity. One must include directional information in order to fully describe the velocity of the object.

When does acceleration occur?
Acceleration occurs when velocities change because the speed changes (what we normally think of as acceleration in a car), because the direction changes, or because both events occur at the same time. It is defined as the rate of change of velocity and is measured in meters per second per second (m/s2).

What is force, and what are the two different types?
Force is defined as a push or pull that acts on an object. The first type of force is Contact Force, which involves physical contact between objects; e.g., the force involved in hitting a ball, pulling a wagon, compressing a spring, etc. The second kind of force is field force, which doesn't involve physical contact between objects; e.g., gravitational force and electromagnetic force.

Sample Video Transcript

Below is a transcript of the video sample provided for this module:

To better understand the physics of motion, it is essential to first understand the meaning of the primary terms. In the following slides, these terms will be used and described. Force is any interaction which tends to change the motion of an object. Mass refers to how much matter is in an object. It is a property of a physical body, which determines the body's resistance to being accelerated by a force. Gravity is the force of attraction by which objects tend to fall or be pulled toward the center of the earth. Weight is the force exerted on a body by gravity. Friction is the surface resistance to relative motion. Speed is the distance traveled per unit of time. Velocity is the rate at which an object changes its position. Acceleration is the measurement of change in an object's velocity. And momentum is the product of mass multiplied by velocity.