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.
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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.
