Question

A driver of a car traveling 12 m/s applies the breaks. After 2 seconds the speed drops to 8 m/s what is the cars acceleration?

Answer 1

Acceleration value of car = -2
`m/s^2`

Step-by-step explanation:

We have equation of motion, v = u + at, where v is the final velocity, u is the initial velocity, a is the acceleration and t is the time taken.

Here a car is traveling at 12 m/s, so initial velocity = 12 m/s

After 2 seconds the speed drops to 8 m/s, so final velocity = 8 m/s

Time taken = 2 seconds

Substituting

8 = 12 + a * 2

2a = -4

a = -2
`m/s^2`

Acceleration value of car = -2
`m/s^2`

Answer 2

Deceleration of the car is 2
`(m)/(s^(2) )`.

Step-by-step explanation:

Given:

initial speed = 12 m/s

final speed = 8 m/s

time = 2 s

To find:

acceleration = ?

Formula used:

According to first kinematic equation:

v = u + a t

Where, v = final speed

u = initial speed

t = time

a = acceleration

Solution:

According to first kinematic equation:

v = u + a t

Where, v = final speed

u = initial speed

t = time

a = acceleration

8 = 12 + 2 a

-4 = 2 a

a = -2
`(m)/(s^(2) )`

The negative sign implies that it is deceleration. Thus, deceleration of the car is 2
`(m)/(s^(2) )`.