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Saturday, 31 October

JEE Main 2021 · PhysicsMultiple choiceDiagram basedHardMulti-step

JEE Main 26 February 2021, Shift 2, Physics Q19

Question 19 of 90 in this shift, Physics question 19 of 30, Section A.

An inclined plane making an angle of 30∘30^\circ with the horizontal is placed in a uniform horizontal electric field 200 NC200\ \frac{N}{C} as shown in the figure. A body of mass 1 kg and charge 5 mC is allowed to slide down from rest at a height of 1 m. If the coefficient of friction is 0.2, find the time taken by the body to reach the bottom. [g = 9.8 m/s2^2; sin⁡30∘=12\sin 30^\circ = \frac{1}{2}; cos⁡30∘=32\cos 30^\circ = \frac{\sqrt{3}}{2}]

The figure, in words

Right triangle inclined plane, angle 30∘30^\circ marked at the lower left vertex, vertical side on the right marked 1 m with a double-headed arrow. A small block labelled 1 kg, 5 mC sits on the inclined surface near the top. A horizontal arrow labelled E = 200 N/C points to the right above the left part of the incline.
  1. (1)2.3 s
  2. (2)1.3 sOfficial answer
  3. (3)0.92 s
  4. (4)0.46 s

Official answer

Option 2

NTA final key.

Chapter
Electric Charges and Fields
Topic
Friction
Idea tested
Motion Down a Rough Incline

Same idea in other shifts

Asked 4× in all
  1. 4 Apr 2026, Shift 1 · Q28The time taken by a block of mass mm to slide down from the highest point to the lowest point on a rough inclined plane is 50 %50\ \% more…MediumSingle correct
  2. 6 Apr 2026, Shift 2 · Q46A block takes tt time to slide down a plane inclined at 45∘45^\circ to the horizontal. If the surface is made smooth (frictionless), the…MediumNumerical value
  3. 8 Apr 2024, Shift 2 · Q33A given object takes n times the time to slide down 45∘45^\circ rough inclined plane as it takes the time to slide down an identical…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.