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Saturday, 31 October

JEE Main 2021 · PhysicsNumerical answerNumerical valueHardMulti-step

JEE Main 17 March 2021, Shift 2, Physics Q22

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

A boy of mass 4 kg is standing on a piece of wood having mass 5 kg. If the coefficient of friction between the wood and the floor is 0.5, the maximum force that the boy can exert on the rope so that the piece of wood does not move from its place is ____________ N. (Round off to the Nearest Integer) [Take g=10 ms−2\mathrm{g=10\ ms^{-2}}]

The figure, in words

A rope-and-pulley system hung from a horizontal ceiling bar: three pulleys (one upper left, one upper right, one lower right). A boy stands on a hatched block of wood resting on the floor and pulls the rope, labelled F, which goes up to the upper left pulley, across the top to the upper right pulley, down to the lower right pulley and back horizontally to the wood block. Tension T is marked with arrows on each rope segment; R (upward arrow, with a downward arrow below the block) is marked at the block, and a leftward arrow is drawn at the left end of the floor line.

Official answer

30

NTA final key.

Chapter
Laws of Motion
Topic
Friction
Idea tested
Impending Motion Analysis

Same idea in other shifts

Asked 2× in all
  1. 26 Feb 2021, Shift 1 · Q21As shown in the figure, a block of mass 3\sqrt{3} kg is kept on a horizontal rough surface of coefficient of friction…MediumNumerical valueHas a figure

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.