Motion is basically a change in the object's position relative to a reference point, but what is it?
How do you know the train below is moving? You see the trees go by and the curtains bounce. These are reference points
Reference points help us figure out if something is in motion.
One of the ways we measure an object's motion is to measure its distance and displacement.
We usually measure them in meters (m), but it can change depending on how large the distance/displacement is
Knowing the difference between distance and displacement be important for formulas later on (just ask the 9th grade teachers!)
Another way we measure motion is to figure out how fast an object is travelling. This is called speed
Speed is the the distance an object traveled divided by the time it took the object to travel
We can measure speed in two different ways:
instantaneously
average
Instantaneous speed is at a specific "instant" (when you check your speedometer in a car). To figure out instantaneous speed, we need to use displacement
Average speed is the average speed an object is travelling during the total time
Another way we measure the motion of an object is velocity.
Velocity is the change in speed divided by the change in time
Speed and velocity are usually measured in m/s
Speed and velocity sound similar, but there is one BIG BIG difference: velocity has a direction
Saying you are driving 70 miles per hour (speed) is different than saying driving 70 miles per hour on I-75 North (velocity)
Because of this, it is possible to have a negative velocity (travelling backward)
The last way we measure the motion of an object is acceleration.
Acceleration is the change in velocity divided by the change in time
Because velocity has a direction, acceleration has a direction too
Check out this simulation!
**NOTE: Mobile users might need to switch to "desktop mode" to fully view the animation**