A boat is moving at the rate of 15.0 meters per second. It's speed is then decreased uniformly to 3.0 meters per second. It takes 4 seconds for the speed to decrease. What is the magnitude of the deceleration of the car ?

Explanation:

Given:

Initial velocity: 15 m/s

Final velocity: 3 m/s

Time: 4 s

Equation to be used is:

v = u + a*t

3 = 15 + a*(4)

a = -3 m/s^2

Since a is negative, the car is decelerating.

General note for kinematic equation questions:

These equations are built around 5 quantities:

s = displacement

u = initial velocity

v = final velocity

t = time

a = acceleration

Before starting, list down what quantities are given in the question and what quantities are asked. This will help you choose the right kinematic equation to solve the problem.