Question

A car is moving with a speed of 15 m/s on a straight road is brought to rest while covering a
distance of 3/20 km. If mass of car is 600 kg. Find the retarding force on the car.
(A) 200 N
(B) 225 N
(C) 450 N
(D) none of these
​

Answer 1

Answer:

d) None of these

Explanation:

u=15m/s

v=0

s=distance travelled=3/20km

By newtons third law of motion,

v^2-u^2=2as

0-15^2=2×a×3/20

a=-225×10/3 m/s.

RETARDING FORCE=MASS×DECELERATION

= 600×-225×10/3

=-450000N

Answer 2

Answer:

C) 450 N

Explanation:

Initial velocity(u)=15 m/sec

Car is brought to rest so it's final velocity(u)=0 m/sec

Distance travelled(s)=3/20 km=150 m

Applying v^2 = u^2 + 2as

0^2 = 15^2 + 2 × a × 150

-225=300a

-225/300=a

a=-225/300

Mass of car=600 kg

Force=ma

Force=600 × -225/300

=2 × -225

=-450 N

Wasn't this a 8th class big bang edge fiitjee question?

I also went to give it..i'm in 8th too