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A small block slides down on a smooth inclined plane starting from rest at time t=0t=0. Let SnS_n be the distance traveled by the block in the interval t=n1t=n-1 to t=nt=n. Then the ratio SnSn+1\frac{S_n}{S_{n+1}} is:

A

\frac{2n+1}{2n-1}

B

\frac{2n}{2n-1}

C

\frac{2n-1}{2n}

D

\frac{2n-1}{2n+1}

Step-by-Step Solution

  1. Identify the Formula: The distance traveled by a body undergoing uniformly accelerated motion in the nn-th second (interval from t=n1t = n-1 to t=nt = n) is given by the formula: Sn=u+a2(2n1)S_n = u + \frac{a}{2}(2n - 1) where uu is the initial velocity and aa is the acceleration.
  2. Apply Conditions: The block starts from rest, so u=0u = 0. The acceleration aa is constant (gsinθg \sin \theta on an incline). Thus: Sn=a2(2n1)S_n = \frac{a}{2}(2n - 1)
  3. Calculate for (n+1)-th Interval: For the next interval (t=nt = n to t=n+1t = n+1), we substitute nn with (n+1)(n+1): Sn+1=a2[2(n+1)1]=a2(2n+21)=a2(2n+1)S_{n+1} = \frac{a}{2}[2(n + 1) - 1] = \frac{a}{2}(2n + 2 - 1) = \frac{a}{2}(2n + 1)
  4. Calculate Ratio: SnSn+1=a2(2n1)a2(2n+1)=2n12n+1\frac{S_n}{S_{n+1}} = \frac{\frac{a}{2}(2n - 1)}{\frac{a}{2}(2n + 1)} = \frac{2n - 1}{2n + 1}
  5. Context: This is a generalization of Galileo's law of odd numbers found in NCERT .
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