If something is in a different place than it was.
You would buy a motion sensor alarm if you wanted to know if someone was in your house while you were asleep. Also if you wanted to bust your kids sneaking out.
velocity
motion
Inertia,
translatory motion
Newton's first law of motion tells us that an object in motion stays in motion. When someone slams on the breaks in the car, the breaks can stop the car, but can't stop the driver from being thrown forward.
An object in motion will continue to stay in motion until acted upon by another force.
A catalyst is something or someone who sets things into motion.
When someone is like happy and sad
you need to know where the object is and where it is after a period of time
velocity
Velocity