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Two balls are dropped from heights h and 2h respectively from the earth surface. The ratio of time of these balls to reach the earth is:

A

1 : \sqrt{2}

B

\sqrt{2} : 1

C

2 : 1

D

1 : 4

Step-by-Step Solution

  1. Principle: For a body in free fall starting from rest (u=0u=0), the distance fallen (hh) in time (tt) is given by the kinematic equation: h=ut+12gt2h=12gt2h = ut + \frac{1}{2}gt^2 \Rightarrow h = \frac{1}{2}gt^2
  2. Relation: This implies that time is proportional to the square root of the height: t=2hgtht = \sqrt{\frac{2h}{g}} \Rightarrow t \propto \sqrt{h} .
  3. Calculation: For the first ball (h1=hh_1 = h): t1ht_1 \propto \sqrt{h} For the second ball (h2=2hh_2 = 2h): t22ht_2 \propto \sqrt{2h}
  4. Ratio: t1t2=h2h=12\frac{t_1}{t_2} = \frac{\sqrt{h}}{\sqrt{2h}} = \frac{1}{\sqrt{2}} The ratio is 1:21 : \sqrt{2}.
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