Question

Why acceleration related with velocity not with speed ?

Answer 1

this is because acceleration and velocity have direction means they are vector quantities

whereas speed is a scalar quantity it doesn't have any direction

eg :

if a car is moving from left to right at 5km/h

its speed is 5km/h and its velocity is also 5km/h

if the same car is returning from right to left at 5km/h

its speed is 5km/h but velocity is - 5km/h ( as the car is moving in the opposite direction)

similarly, acceleration also have direction that's why velocity and acceleration are related

but not with speed