JEE Main 2021 · 24 February · evening · Single correct · +4 / −1
When a particle executes SHM, the nature of graphical representation of velocity as a function of displacement is :
- (a) circular
- (b) straight line
- (c) parabolic
- (d) elliptical
Answer and solution
Answer (d) elliptical
Solution
Physics sir · 4 steps
Write v in terms of x, square both sides, and the curve tells you its own shape.
- Velocity formula. For SHM with amplitude A and angular frequency ω, the velocity at displacement x is v = ±ω√(A² - x²).
- Square and rearrange. Squaring gives v² = ω² (A² - x²). Divide both sides by ω² A² and bring the x term across.
x²/A² + v²/(ω² A²) = 1
- Read the shape. This is the standard form of an ellipse with semi-axes A along x and ω A along v. It would look like a circle only if the two semi-axes happened to be equal on the graph, which is not true in general.
- So. The velocity versus displacement graph is elliptical, which is option (d).
The idea to keep. In SHM, v against x is an ellipse, because x² and v² add up to a constant. Remember that a against x is a straight line through the origin.
Answer from the NTA final answer key. Solution by PrepWiser.