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Friday, 9 October

JEE Main 2021 · PhysicsNumerical answerNumerical valueMediumMulti-step

JEE Main 18 March 2021, Shift 1, Physics Q22

Question 22 of 90 in this shift, Physics question 22 of 30, Section B.

A ball of mass 10 kg moving with a velocity 10310\sqrt{3} m/s along the xx-axis, hits another ball of mass 20 kg which is at rest. After the collision, first ball comes to rest while the second ball disintegrates into two equal pieces. One piece starts moving along yy-axis with a speed of 10 m/s. The second piece starts moving at an angle of 30° with respect to the xx-axis. The velocity of the ball moving at 30° with xx-axis is xx m/s. The configuration of pieces after collision is shown in the figure below. The value of xx to the nearest integer is __________.

The figure, in words

Piece 1 moves along +y axis with v1 = 10 m/s; piece 2 moves with speed v2 at 30 degrees below the +x axis (in fourth quadrant).

Official answer

20

NTA final key.

Chapter
System of Particles and Rotational Motion
Topic
Collisions
Idea tested
Momentum in Explosions

Same idea in other shifts

Asked 4× in all
  1. 8 Apr 2024, Shift 1 · Q33A stationary particle breaks into two parts of masses mAm_A and mBm_B which move with velocities vAv_A and vBv_B respectively. The ratio…EasySingle correct
  2. 31 Jan 2024, Shift 1 · Q35An artillery piece of mass M1M_1 fires a shell of mass M2M_2 horizontally. Instantaneously after the firing, the ratio of kinetic energy…EasySingle correct
  3. 29 Jun 2022, Shift 1 · Q32A body of mass M at rest explodes into three pieces, in the ratio of masses 1:1:21 : 1 : 2. Two smaller pieces fly off perpendicular to each…EasySingle correct

Question text from the official JEE Main paper published by NTA; answer from the final answer key. Chapter, topic and idea tags, difficulty and skill are Lumi’s. This question needs a figure we do not reproduce; it is described in words above. Lumi analyses 42 of the 174 JEE Main shifts held from 2017 to 2026.