# MCQ

11. we know that , total time of flight is ,

$T=\frac{2u\mathrm{sin}90\xb0}{g}\left[\alpha =90\xb0\right]\phantom{\rule{0ex}{0ex}}=\frac{2u}{g}=\frac{2\times 100}{10}=20s$

12. Here from the equation of motion we have ,

$h=ut+\frac{1}{2}g{t}^{2}\phantom{\rule{0ex}{0ex}}=0+\frac{1}{2}g{t}^{2}\left[u=0\right]\phantom{\rule{0ex}{0ex}}=\frac{1}{2}\times 10\times {4}^{2}\phantom{\rule{0ex}{0ex}}=5\times 16\phantom{\rule{0ex}{0ex}}=80m$

13.When an object falls freely to the earth then the direction of force of gravity is in the same direction of motion of the object .

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