Question

A car accelerates uniformly from rest to attain a speed of 20 m/s after covering a distance of 80 m. It then decelerates uniformly and comes to rest after covering further a distance of 160 m. The total time taken for this journey is....
Pls full solution

Answer 1

$\underline\bold\pink{\huge{HELLO\:DEAR}}$

1️⃣

u = 0 m/s.
v = 20 m/s.
S = 80 m.

Applying third equation of motion,
v²=u²+2aS
=> (20)²=0²+2×a×80
=> 400=160a
=> a = 400/160 = 2.5 m/s².

Applying first equation of motion,
v=u+at
=> 20=0+2.5×t
=> t = 20/2.5 = 8 s.

2️⃣

u = 20 m/s.
v = 0 m/s.
S = 160 m.

Applying third equation of motion,
v²=u²+2aS
=> 0²=20²+2×a×160
=> 0=400+320a
=> 400+320a=0
=> 320a = - 400
=> a = -400/320 = -1.25 m/s² (retardation or negative acceleration)

Now, again by applying the first equation of motion, we get :
v=u+at
=> 0 = 20-1.25×t
=> 20 - 1.25t=0
=> -1.25t = -20
=> t = 20/1.25 = 16 s.

Total Time for this journey = (8+16) s = 24 s.

⭐ THIS ANSWER WILL BE CLEAR TO YOU. NO DIFFICULTIES ARE THERE IN THE ABOVE ANSWER.
⭐ IF YOU HAVE ANY DOUBTS, FEEL FREE TO ASK ME AGAIN.
⭐ ALWAYS BE BRAINLY...........!!!!!!!!!