JEE Mains · Physics · STD 11 - 2. motion in straight line
When a ball is dropped into a lake from a height \(4.9 \,m\) above the water level, it hits the water with a velocity \(v\) and then sinks to the bottom with the constant velocity \(v\). It reaches the bottom of the lake \(4.0,s\) after it is dropped. The approximate depth of the lake is ............ \(m\)
- A \(19.6\)
- B \(29.4\)
- C \(39.2\)
- D \(73.5\)
Answer & Solution
Correct Answer
(B) \(29.4\)
Step-by-step Solution
Detailed explanation
\(v = \sqrt{2gh}\) \(v = \sqrt{2 \times 9.8 \, m/s^2 \times 4.9 \, m}\) \(v = 9.8 \, m/s\) \(t_1 = \frac{v}{g}\) \(t_1 = \frac{9.8 \, m/s}{9.8 \, m/s^2}\) \(t_1 = 1.0 \, s\) \(t_2 = T_{total} - t_1\) \(t_2 = 4.0 \, s - 1.0 \, s\) \(t_2 = 3.0 \, s\) \(h_{lake} = v \times t_2\)…
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