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Friday, 9 October

JEE Main 2020 · PhysicsMultiple choiceDiagram basedMediumCalculation

JEE Main 2 September 2020, Shift 1, Physics Q8

Question 8 of 75 in this shift, Physics question 8 of 25.

A cylindrical vessel containing a liquid is rotated about its axis so that the liquid rises at its sides as shown in the figure. The radius of vessel is 5 cm and the angular speed of rotation is ω rad s−1\omega\ \mathrm{rad\ s^{-1}}. The difference in the height, hh (in cm) of liquid at the centre of vessel and at the side will be :

The figure, in words

Cylindrical vessel (width 10 cm) rotating about its vertical axis with angular speed omega; liquid surface is a paraboloid, lower at centre and higher at the sides; h is the height difference between the side and centre.
  1. (1)2ω225g\frac{2\omega^{2}}{25g}
  2. (2)25ω22g\frac{25\omega^{2}}{2g}Official answer
  3. (3)5ω22g\frac{5\omega^{2}}{2g}
  4. (4)2ω25g\frac{2\omega^{2}}{5g}

Official answer

Option 2

NTA final key (Sep 2020).

Chapter
Mechanical Properties of Fluids
Topic
Fluid Dynamics
Idea tested
Surface Profile of a Rotating Fluid

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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.