All motion is relative to some fixed point or object. Speed is a measurement of that change in position over time. Velocity is speed in a given direction. Vectors help to determine the sum of velocities. Acceleration is the increase in speed or velocity over a period of time.
Deceleration is the decrease of speed or velocity over time.
It depends on the speed It depends on your point of view It depends on your relatives 2. Speed has direction Velocity has direction 3. As an aid in calculating the sum of velocities To accelerate velocities To make triangles If you got all three correct, you are on your way to becoming a champion in science. If you had problems, you had better look over the material again. I will try to get back to you as soon as possible.