KinematicsHard
Question
A particle moves in the xy plane and at time t is at the point (t2, t3 - 2t). Then : -
Options
A.At t = 2/3 s, directions of velocity and acceleration are perpendicular
B.At = 0, direction of velocity and acceleration are perpendicular
C.At t = 
s, particle is moving parallel to x - axis
s, particle is moving parallel to x - axisD.Velocity of line particle at t = 9s is 8 mn / sec.
Solution
= t2 î + (3t2 - 2) ĵ ;
= 
= 2tî + (3t2 - 2) ĵ
= 
2î + 6tĵ
. 
= 4t + 18t3 - 12t = 0 (For ⊥) ∴ t = ± 2 / 3, 0.
For parallel to x - axis ⇒
= 0 ⇒ 
∴ at t =
sec it become zero so (c) 
(4, 4) = 2î + 6 × 2ĵ = 2î + 12ĵCreate a free account to view solution
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