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Free fall
Appears in
Concepts tested here
- Distances in equal time intervals
- Momentum and height of fall
All Questions
2013 NEET 1 question
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A stone falls freely under gravity. It covers distances $h_1$, $h_2$ and $h_3$ in the first 5 seconds, the next 5 seconds and the next 5 seconds respectively. The relation between $h_1$, $h_2$ and $h_3$ is:$h_1 = \frac{1}{2}g(5)^2$, $h_1 + h_2 = \frac{1}{2}g(10)^2$ and $h_1 + h_2 + h_3 = \frac{1}{2}g(15)^2$
So $h_1 : h_2 : h_3 = 1 : 3 : 5$, i.e. $h_1 = \frac{h_2}{3} = \frac{h_3}{5}$
2012 AIPMT-MAINS 1 question
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A stone is dropped from a height h. It hits the ground with a certain momentum P. If the same stone is dropped from a height 100% more than the previous height, the momentum when it hits the ground will change bySpeed on hitting the ground: $v = \sqrt{2gh}$, so momentum $P = m\sqrt{2gh} \propto \sqrt h$
The new height is 100% more, i.e. 2h.
$\frac{P'}{P} = \sqrt{\frac{2h}{h}} = \sqrt2 \Rightarrow P' = \sqrt2P = 1.41P$
Change in momentum $= \frac{P' - P}{P}\times100 = 41\%$