I can't do all your physics homework but I can give you some hints. "Speed" is a scalar measure (it's a value, but measured against convention - if I say "the thermometer says it's 45 degrees" that is a scalar description. If I say "45 degrees and rising at 1 degree per hour", that's a vectorial description). "Velocity" is vectorial measure - because it has the two requirements needed to be called a vector: magnitude (speed) and direction. A change in velocity of an object is called "acceleration" (even though "slowing" is loosely called "deceleration", it's more precisely called "negative acceleration"). Velocity and acceleration have a mathematical relationship - check out what a "function" is, how it's written to express velocity (which can be graphed against a horizontal time-line) and what the "first derivative" of velocity is (using Newton's notation, it looks like this: f'(x) = etc.).