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Change of position is Motion, and we can see Motion everywhere we look. Anytime our position changes, we are in Motion.
Example: The Earth revolving around the sun and turning the page of a textbook.
Motion is relative because it is always described in relation to a reference point.
Example: We can not see or feel the Earth spinning even if it rotates more than 1,000 miles per hour at the equator because everything around us is rotating along with the Earth. That means nothing is moving from our reference point.
SPEED AND VELOCITY
The distance something travels in a certain amount of time is the speed.
The distance measured in METERS (m)
Time measured in SECONDS (s)
Speed measured in METERS PER SECOND (m/s)
When we drive or travel by car, it's Motion. Our speed of drive or travel does not stay at the same speed all the time. Sometimes it can move faster, or sometimes, it can move slower between the distance. In such situations, we need to measure the average speed.
The total distance something has traveled divided by the total time it has traveled is the average speed.
The speed at a particular given moment is called Instantaneous speed.
Velocity is the speed in a specific direction. So a change in Velocity means either a change in DIRECTION or a change in SPEED.
Example: When a vehicle turns a bend, it changes Velocity, even if it keeps the same speed.
Acceleration is the rate at which Velocity changes. When an object changes Velocity, it's accelerating. It can be speeding up
, slowing down
, or changing the direction
Final and initial (starting) velocities are measured in METERS PER SECOND (m/s)
Time is measured in SECONDS(s)
Acceleration is therefore measured in units of METERS PER SECOND SQUARED(m/s2).
Acceleration is positive when it is moving in the same direction as the object's Motion. Speeding up is the positive acceleration.
Acceleration is negative when it is in the opposite direction of the object's Motion, which means the object is slowing down.
The negative acceleration is also called deceleration.