Question:

At time t = 0 a particle starts travelling from a height \(7\hat z cm\) in a plane keeping \(z\) coordinate constant. At any instant time it's position along the \(x\) and \(y\) directions are defined as \(3t\) and \(5t^3\) respectively. At \(t = 1s\) acceleration of the particle will be

Updated On: Jul 8, 2024
  • \(-30 \hat {y}\)
  • \(30\hat {y}\)
  • \(3 \hat {x}+ 15\hat {y}\)
  • \(3\hat{x}^+15\hat{y}+7\hat{z}\)
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The Correct Option is B

Solution and Explanation

\(\vec r=3t\hat {i}+5t^3\hat{j}+7\hat{k}\) 
\(\frac{d^2\vec r}{dt^2}=30t\hat{j}\)   At  \(t=1\) 
⇒ \(\frac{d^2\vec r}{dt^2}\)\(30\hat{j}\)
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Concepts Used:

Motion in a Plane

It is a vector quantity. A vector quantity is a quantity having both magnitude and direction. Speed is a scalar quantity and it is a quantity having a magnitude only. Motion in a plane is also known as motion in two dimensions. 

Equations of Plane Motion

The equations of motion in a straight line are:

v=u+at

s=ut+½ at2

v2-u2=2as

Where,

  • v = final velocity of the particle
  • u = initial velocity of the particle
  • s = displacement of the particle
  • a = acceleration of the particle
  • t = the time interval in which the particle is in consideration