Question:

The time taken by a body to slide down the smooth inclined plane is \(4\) sec. The time taken by a body to slide \(1/4^{th}\) of the length of the plane is

Show Hint

For uniformly accelerated motion from rest, distance is proportional to \(t^2\).
  • \(1\) sec
  • \(2\) sec
  • \(3\) sec
  • \(0.5\) sec
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The Correct Option is B

Solution and Explanation

Concept:
For motion starting from rest with uniform acceleration: \[ s=\frac{1}{2}at^2 \]

Step 1:
Since the plane is smooth, acceleration down the plane is constant.

Step 2:
Distance travelled is proportional to square of time: \[ s\propto t^2 \]

Step 3:
Let full length of plane be \(L\), and time taken for full length be: \[ T=4\text{ sec} \]

Step 4:
For \(1/4\) of the length: \[ \frac{s}{L}=\frac{1}{4} \] \[ \frac{t^2}{T^2}=\frac{1}{4} \]

Step 5:
\[ \frac{t}{T}=\frac{1}{2} \] \[ t=\frac{T}{2} \] \[ t=\frac{4}{2}=2\text{ sec} \] \[ \boxed{2\text{ sec}} \]
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