Physics Circle home Student Login

Home›Chapters›Work, Energy and Power PYQs›Collisions›Question 6

JEE Main 2021 (31 Aug, Shift 2) · Collisions

Collisions question from JEE Main 2021 (31 Aug, Shift 2)

Q6JEE Main 2021 · 31 AUG · SHIFT 2Medium

Collisions

A block moving horizontally on a smooth surface with a speed of 40 m/s splits into two parts with masses in the ratio of 1: 2. If the smaller part moves at 60 m/s in the same direction, then the fractional change in kinetic energy is :-

Show answer and solution

Answer: (c)

  1. Masses mm and 2m2m: 3m(40)=m(60)+2m v⇒v=30 m/s3m(40) = m(60) + 2m\,v \Rightarrow v = 30\text{ m/s}
  2. Ki=12(3m)(40)2=2400mK_i = \frac{1}{2}(3m)(40)^2 = 2400m
  3. Kf=12m(60)2+12(2m)(30)2=1800m+900m=2700mK_f = \frac{1}{2}m(60)^2 + \frac{1}{2}(2m)(30)^2 = 1800m + 900m = 2700m
  4. ΔKKi=3002400=18\frac{\Delta K}{K_i} = \frac{300}{2400} = \frac{1}{8}
  5. So the answer is (c) 18\frac{1}{8}.
Report a mistake

More questions on Collisions