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Saturday, 31 October

JEE Main 2020 · PhysicsMultiple choiceSingle correctHardMulti-step

JEE Main 4 September 2020, Shift 1, Physics Q4

Question 4 of 75 in this shift, Physics question 4 of 25.

Blocks of masses m, 2m, 4m and 8m are arranged in a line on a frictionless floor. Another block of mass m, moving with speed vv along the same line (see figure) collides with mass m in perfectly inelastic manner. All the subsequent collisions are also perfectly inelastic. By the time the last block of mass 8m starts moving the total energy loss is p% of the original energy. Value of ‘p’ is close to :

The figure, in words

Five hatched square blocks in a row on a horizontal line, labelled left to right m, m, 2m, 4m, 8m; an arrow pointing right labelled vv above the leftmost block.
  1. (1)37
  2. (2)77
  3. (3)87
  4. (4)94Official answer

Official answer

Option 4

NTA final key (Sep 2020).

Chapter
Work, Energy and Power
Topic
Collisions
Idea tested
Successive 1D Collisions

Same topic in other shifts

All Collisions questions
  1. 3 Apr 2025, Shift 2 · Q29Consider two blocks A and B of masses m1=10m_1 = 10 kg and m2=5m_2 = 5 kg that are placed on a frictionless table. The block A moves with a…MediumSingle correctHas a figure
  2. 4 Apr 2024, Shift 1 · Q35If a rubber ball falls from a height h and rebounds upto the height of h/2. The percentage loss of total energy of the initial system as…EasySingle correct
  3. 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
  4. 8 Apr 2024, Shift 1 · Q34A player caught a cricket ball of mass 150 g moving at a speed of 20 m/s. If the catching process is completed in 0.1 s, the magnitude of…EasySingle correct
  5. 9 Apr 2024, Shift 2 · Q33A nucleus at rest disintegrates into two smaller nuclei with their masses in the ratio of 2:12:1. After disintegration they will move :EasySingle correct
  6. 1 Feb 2024, Shift 1 · Q35A simple pendulum of length 1 m has a wooden bob of mass 1 kg. It is struck by a bullet of mass 10−210^{-2} kg moving with a speed of…MediumSingle 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 108 of the 174 JEE Main shifts held from 2017 to 2026.