Q7 / 72 · NTA Abhyas (JEE Main) 2020 · Physics · Motion In Two Dimensions

The position vector of the particle is rt=acos⁡ωti^+asin⁡ωtj^, where a and ω are real constants of suitable dimensions. The acceleration is

  • Correct answer
    A
    Perpendicular to the velocity
  • B
    Parallel to the velocity
  • C
    Directed away from the origin
  • D
    Perpendicular to the position vector

Solution

Given that, rt=acos⁡ωti^+a sin⁡ωtj^

∵v→=drtdt=-aωsin⁡ωt i^+aωcos⁡ωt i^j

a→=dv→dt=-aω2cos⁡ωti^-aω2cos⁡ωtj^

a→.v→=a2ω3sin⁡ωtcos⁡ωt-a2ω3sin⁡ωtcos⁡ωt

⇒ a→.v→=0

Above result implies that acceleration is perpendicular to velocity.

Hence, the correct answer is option: 'A'.

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