Question

a train was moving at a speed of 20ms-1. at the brakes, It's slowed down and stopped at a distance of 300m. slow down and what is the required time?​

Answer 1

☀️ Given that: A train was moving with a speed of 20 m/s and after applying brakes it is slowed down and stopped at a distance of 300m

     Need to find: Time required to stop

Must know:

• Final velocity of train will be 0 m/s as it is stopped by applying brakes.

• Acceleration will be negative ( Retardation ) as the train is being slowed down.

• According to second equation of motion v² = u² + 2as

• According to first equation of motion v = u + at

Where,

v is final velocity ( 0m/s )

u is initial velocity ( 20m/s )

a is acceleration

s is distance travelled ( 300m )

t is time taken

Solution:

• Finding acceleration-

→ v² = u² + 2as

→ 0² = 20² + 2 × a × 300

→ 0 = 400 + 600a

→ -400 = 600a

→ a = -400/600

→ a = -2/3 m/s²

• Finding the time taken-

→ v = u + at

→ 0 = 20 + ( - 2/3 × t )

→ -20 = -2/3 × t

→ t = -20 × -3/2

→ t = -10 × -3  

→ t = 30s

⠀━━━━━━━━━━━━━━━━━━━  

• Henceforth, the time taken to stop after application of brakes is 30 seconds