JEE Main 2021 · 17 March · evening · Single correct · +4 / −1
Two particles A and B of equal masses are suspended from two massless springs of spring constants K₁ and K₂ respectively. If the maximum velocities during oscillations are equal, the ratio of the amplitude of A and B is
- (a) K₁/K₂
- (b) √(K₁/K₂)
- (c) K₂/K₁
- (d) √(K₂/K₁)
Answer and solution
Answer (d) √(K₂/K₁)
Solution
Physics sir · 3 steps
Maximum speed is amplitude times omega, so equal speeds mean the stiffer spring gets the smaller amplitude.
- Maximum speed. In SHM the particle is fastest at the mean position, where vₘₐₓ = Aω. For a mass on a spring, ω = √(K/m).
- Set them equal. Both masses are m, so equal maximum speeds give A₁√(K₁/m) = A₂√(K₂/m). The m cancels from both sides.
A₁/A₂ = ω₂/ω₁ = √(K₂/K₁)
- So. The ratio of the amplitudes of A and B is √(K₂/K₁), which is option (d).
The idea to keep. Whenever vₘₐₓ is fixed, amplitude goes as 1/ω. For springs that means A ∝ 1/√K, so a stiffer spring oscillates through a smaller distance.
Answer from the NTA final answer key. Solution by PrepWiser.