COMPASSLearning
RegisterLogin

JEE Main · 2025 · 08 Apr 2025 · Shift 2 · Fluid Mechanics

WhatsApp Email
A cube having a side of 10 cm with unknown mass and 200 gm mass were hung at two ends of an uniform rigid rod of 27 cm long. The rod along with masses was placed on a wedge keeping the distance between wedge point and 200 gm weight as 25 cm. Initially the masses were not at balance. A beaker is placed beneath the unknown mass and water is added slowly to it. At given point the masses were in balance and half volume of the unknown mass was inside the water.
(Take the density of unknown mass is more than that of the water, the mass did not absorb water and water density is .) The unknown mass is ______ kg.

Answer: 3

Solution

The cube of side has volume , so when half is submerged the displaced water volume is and the buoyant force is . The unknown mass hangs from the wedge, while the mass is away on the other side. Balancing torques about the wedge, , which gives and . The unknown mass is .

JEE Main · 2025 · 08 Apr 2025 · Shift 2 · Integer answer

Practise more: all JEE Main PYQs on Fluid Mechanics →

More JEE Main questions on Fluid Mechanics

  1. Given below are two statements:
    Statement I: Pressure of fluid is exerted only on a solid surface in contact as the fluid-pressure does not exist everywhere in a still fluid.
    Statement II: Excess potential energy of the molecules on the surface of a liquid, when compared to inter …
    JEE Main 2026View solution →
  2. When a part of a straight capillary tube is placed vertically in a liquid, the liquid raises upto certain height h. If the inner radius of the capillary tube, density of the liquid and surface tension of the liquid decrease by each, then the height of the liquid in the tube …
    JEE Main 2026View solution →
  3. Surface tension of two liquids (having same densities), and , are measured using capillary rise method utilizing two tubes with inner radii of and where . The measured liquid heights in these tubes are …
    JEE Main 2026View solution →
  4. The terminal velocity of a metallic ball of radius 6 mm in a viscous fluid is . The terminal velocity of another ball of same material and having radius 3 mm in the same fluid will be
    ____ .
    JEE Main 2026View solution →
  5. A small metallic sphere of diameter 2 mm and density g/cm³ is dropped in glycerine having viscosity 10 Poise and density g/cm³ respectively. The terminal velocity attained by the sphere is cm/s.
    ( and m/s²)
    JEE Main 2026View solution →
  6. Sixty four rain drops of radius 1 mm each falling down with a terminal velocity of coalesce to form a bigger drop. The terminal velocity of bigger drop is ______ .
    JEE Main 2026View solution →