Kinematics is the subdivision of physics and it is related to the explanation of all those objects that are in motion. I have the speed of an object say 5ms and the time it takes the object to come to a complete stop say 2s. Deceleration is the final velocity minus the initial velocity with a negative sign in the result because the velocity is dropping.
You can find Claras speed by dividing the distance that she ran by the time it took her to cover that distance.
The object has no friction. How to Calculate Acceleration with Velocity and Distance. The best I can do is get average deceleration over an interval. The red line shows a deceleration from 30 to 0 ms in 10 s.