Question

A car travelling at a speed of 10 m/s is brought to rest in 20 seconds by applying brakes. Calculate the acceleration and distance travelled during this time

Answer 1

u = 10 m/s
v =0
t = 20 sec

From 1st equation of motion,
v =u+at
⇒0 =10 +20a
⇒20a = - 10
⇒a = -0.5 m/s²

now, from 3rd equation,
v²-u² = 2as
⇒(0)²-(20)² = 2×(-0.5)×s
⇒s = 400 m

Answer 2

Given,
Initial Velocity = 10 m/s
Final Velocity =0
Time taken= 20 sec

According to1st equation of motion,
v =u+at
By implying values,
⇒0 =10 +20a
⇒20a = - 10
⇒a = -0.5 m/s²

According to 3rd equation of motion,
v²-u² = 2as
By implying values 
⇒(0)²-(20)² = 2×(-0.5)×s
⇒s = 400 m