Question

A car approaches a stop light going 80 m/s before it comes to a stop. If it does this in 20 seconds, what was its acceleration? *

Answer 1

Answer:

The acceleration of the car is - 4 m/s , where negative sign indicates that there is retardation because final velocity is zerp

Explanation:

Given: car going with velocity 80 m/s approaches a

stop light . It does this in 20 seconds

To find : acceleration

Solution: let , Initial velocity of car = u

Final velocity of car = v

acceleration of car = a

time taken by car = t

According to first eqation of motion :

final velocity of car = initial velocity+ (acceleration× time)

I.e. v= u+at

According to question ,

v = 0m/s

u = 80 m/s

t = 20s

a = ?

0 = 80 + a (20)

20a = - 80

a = -80/20

a = - 4 m/s

Therefore , The acceleration of car is - 4m/s

( Negative sign indicates that there is retardation as the final velocity is zero as car comes to stop at stop light)