Speed and Acceleration

In this search we learned stuff on the web about speed and acceleration.
1) The difference between instantaneous and average speed are: Average speed is the distance traveled in a given period of time. Instantaneous speed is a speed at a certain instant. You are reading your instantaneous speed when looking at your speedometer.
2) Constant speed is when you go the same speed for a period of time. It would travel 300m.
3) Acceleration is a vector quantity that is defined as the rate at which an object changes its velocity. Average Acceleration = Vf-Vi/time. Three units for acceleration are: m/s/s, mi/hr/s, and km/hr/s. It would be going 28 m/s/s.
Part II
1) The slope of a position vs. time graph is the velocity. The velocity increases.
2) -3m/s and the second one is 4m/s
3) The slope of a velocity time graph is acceleration. The line for acceleration will be going on a upward, rightward slope. Deceleration would be the opposite.
Part III
1) It means that the objects do not encounter air resistance. It accelerates downwards at a rate of 9.8 m/s/s
2) The velocity is increasing as it falls downward. Its acceleration as its falling is 3.75 m/s/s.