JEE Main 2021 · 18 March · morning · Single correct · +4 / −1
The position, velocity and acceleration of a particle moving with a constant acceleration can be represented by :
- (a)
- (b)
- (c)
- (d)
Answer and solution
Answer (b)
Solution
Physics sir · 3 steps
Constant a makes v a straight line, and a straight-line v makes x a parabola. Check each panel for that.
- Build the chain. With constant a, the velocity is v = u + at, a straight line of slope a. The position is x = x₀ + ut + 1/2at², a parabola.
- Slopes must agree. The slope of the x–t graph is v, and the slope of the v–t graph is a. A positive constant a means v rises steadily, so the x curve keeps getting steeper and bends upward.
Option x–t v–t Fits constant a > 0? (a) straight line curve getting steeper No: a curved v means a changes, and a straight x means v is constant (b) parabola bending upward straight line rising Yes (c) straight line straight line rising No: a straight x means v is constant, yet v is rising (d) curve bending upward straight line falling No: a falling v needs a < 0, but a is drawn positive - So. Only (b) has a constant a, a straight-line v and a parabolic x, so the answer is (b).
The idea to keep. Each graph is the slope of the one before it. Constant a gives a straight-line v and a parabolic x. Check that each slope matches the next graph.
Answer from the NTA final answer key. Solution by PrepWiser.