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Friday, 9 October

JEE Main 2021 · PhysicsMultiple choiceDiagram basedMediumMulti-step

JEE Main 16 March 2021, Shift 2, Physics Q14

Question 14 of 90 in this shift, Physics question 14 of 30, Section A.

A large block of wood of mass M = 5.99 kg is hanging from two long massless cords. A bullet of mass m = 10 g is fired into the block and gets embedded in it. The (block + bullet) then swing upwards, their centre of mass rising a vertical distance h = 9.8 cm before the (block + bullet) pendulum comes momentarily to rest at the end of its arc. The speed of the bullet just before collision is : (take g=9.8 ms−2g=9.8\ \mathrm{ms^{-2}})

The figure, in words

Ballistic pendulum: block of mass M hung from two long cords; bullet of mass m with velocity v fired horizontally into the block; dashed position shows block raised by vertical height h.
  1. (1)811.4 m/s
  2. (2)821.4 m/s
  3. (3)831.4 m/sOfficial answer
  4. (4)841.4 m/s

Official answer

Option 3

NTA final key.

Chapter
Work, Energy and Power
Topic
Collisions
Idea tested
Ballistic Pendulum

Same topic in other shifts

All Collisions questions
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  2. 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
  3. 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
  4. 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
  5. 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
  6. 8 Apr 2023, Shift 2 · Q40A bullet of mass 0.1 kg moving horizontally with speed 400 ms−1^{-1} hits a wooden block of mass 3.9 kg kept on a horizontal rough…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 42 of the 174 JEE Main shifts held from 2017 to 2026.