NEET 2018 · PhysicsTerminal velocityPrevious Year Question
A small sphere of radius 'r' falls from rest in a viscous liquid. As a result, heat is produced due to the viscous force. The rate of production of heat, when the sphere attains its terminal velocity, is proportional to:
Answer: (A) r⁵. Terminal velocity v_t ∝ r².
- A.r⁵✓
- B.r²
- C.r³
- D.r⁴
Correct Answer
(A) r⁵
Solution & Explanation
Terminal velocity v_t ∝ r². Rate of heat = power dissipated = F_visc·v_t = (6πηr v_t)·v_t = 6πηr·v_t². Since v_t² ∝ r⁴, rate ∝ r·r⁴ = r⁵.
🎯
43,000+ questions in हिंदी & English · one-tap toggle
Open →📚Practice all NEET Physics PYQs chapter-wise →💡Don't get it? Learn the Mechanical Properties Of Fluids concepts →Practice NEET 2018 Physics — free, with instant solutions
43,000+ NEET questions solved step-by-step, chapter-wise, in the MedicNEET app.
More NEET PYQ solutions
PhysA spherical ball is dropped in a long column of a highly viscous liquid. Which curve in the graph shown represents the speed of the ball (v) as a function of time (t)?PhysThe velocity of a small ball of mass M and density d, when dropped in a container filled with glycerine, becomes constant after some time. If the density of glycerine is d/2, then the viscous force acting on the ball will be:PhysTwo small spherical metal balls of equal mass are made from materials of densities ρ₁ and ρ₂ (ρ₁ = 8ρ₂) and have radii 1 mm and 2 mm respectively. They fall vertically from rest in a viscous medium of coefficient of viscosity η and density 0.1ρ₂. The ratio of their terminal velocities is:PhysAn electric dipole with dipole moment 5 × 10⁻⁶ C·m is aligned with the direction of a uniform electric field of magnitude 4 × 10⁵ N/C. The dipole is then rotated through an angle of 60° with respect to the electric field. The change in the potential energy of the dipole is:PhysTwo identical charged conducting spheres A and B have their centres separated by a certain distance. Charge on each sphere is q and the force of repulsion between them is F. A third identical uncharged conducting sphere is brought in contact with sphere A first and then with B and finally removed from both. New force of repulsion between spheres A and B (radii negligible vs separation, treated as point charges) is best given as:PhysThe plates of a parallel plate capacitor are separated by d. Two slabs of different dielectric constant K1 and K2 with thickness 3d/8 and d/2 respectively are inserted in the capacitor. Due to this, the capacitance becomes two times larger than when there is nothing between the plates. If K1/K2 = 1.25, the value of K1 is:PhysA sphere of radius R is carved out of a uniform solid sphere of radius 2R (internally tangent, so its centre is at distance R from the big centre). The ratio of the moment of inertia of the small sphere to that of the remaining part, both about the Y-axis through the big sphere's centre, is:PhysThe Sun rotates once in 27 days. If it expanded to twice its present radius (uniform-density sphere, no external influence), its new period would be about: