Question and Answers Forum

All Questions      Topic List

Properties of Matter Questions

Previous in All Question      Next in All Question      

Previous in Properties of Matter      Next in Properties of Matter      

Question Number 59347 by Tinkutara last updated on 08/May/19

Commented by Tinkutara last updated on 08/May/19

B part only

Commented by Tinkutara last updated on 09/May/19

Yes I am too sad with mine also. Got 4.5k. Yours? But I don't think it's a mistake by NTA, it's an era of tough competition!

Commented by Tinkutara last updated on 09/May/19

Mine was 230 One of my friend got 300 marks but 2.6k AIR What was your marks?

Commented by rahul 19 last updated on 09/May/19

201. U r very lucky! 4530 at 230 marks !!! as far as I know for a rank under 5,000 ,you need 260+ ...

Commented by Tinkutara last updated on 09/May/19

But marks have no meaning now. I got 290 in April but low percentile so January marks were considered. Tmhari kabki %ile maani hai?

Commented by prakash jain last updated on 10/May/19

$$\mathrm{What}\mathrm{shift}\mathrm{you}\mathrm{were}\mathrm{in}\mathrm{April}?$$$$9\mathrm{th}\mathrm{April}\mathrm{morning}?$$$$\mathrm{All}\mathrm{other}\mathrm{shift}\mathrm{would}\mathrm{have}\mathrm{fetched}$$$$\mathrm{you}\mathrm{rank}\mathrm{under}2\mathrm{k}\mathrm{with}290\mathrm{marks}$$

Commented by Tinkutara last updated on 10/May/19

Yes 9th morning in April

Answered by ajfour last updated on 09/May/19

Commented by ajfour last updated on 11/May/19

$$\mathrm{m}\frac{\mathrm{dv}}{\mathrm{dt}}=-\sqrt{2\mathrm{gh}}\frac{\mathrm{dm}}{\mathrm{dt}}(\mathrm{as}\mathrm{m}\frac{\mathrm{dv}}{\mathrm{dt}}={\mathrm{v}}_{\mathrm{rel}}\frac{\mathrm{dm}}{\mathrm{dt}}+{\mathrm{F}}_{\mathrm{ext}})$$$$\left(\rho \mathrm{Ah}\right)\frac{\mathrm{dv}}{\mathrm{dt}}=-\sqrt{2\mathrm{gh}}\left[\frac{\mathrm{d}}{\mathrm{dt}}\left(\rho \mathrm{Ah}\right)\right]$$$$\frac{\mathrm{dv}}{\mathrm{dt}}=-\sqrt{2\mathrm{g}}\times \frac{1}{\sqrt{\mathrm{h}}}\frac{\mathrm{dh}}{\mathrm{dt}}....\left(\mathrm{i}\right)$$$$\mathrm{further}$$$$-\frac{\mathrm{A}}{100}\sqrt{2\mathrm{g}\frac{\mathrm{H}}{4}}=\mathrm{A}\frac{\mathrm{dh}}{\mathrm{dt}}$$$$\mathrm{or}\frac{\mathrm{dh}}{\mathrm{dt}}=-\frac{1}{100}\sqrt{\frac{\mathrm{gH}}{2}}$$$$\frac{\mathrm{dv}}{\mathrm{dt}}=\sqrt{2\mathrm{g}}\times \frac{2}{\sqrt{\mathrm{H}}}\times \frac{1}{100}\sqrt{\frac{\mathrm{gH}}{2}}$$$$\mathrm{a}=\frac{\mathrm{g}}{50}$$$$\mathrm{And}\mathrm{from}\left(\mathrm{i}\right)$$$$\mathrm{dv}=-\sqrt{2\mathrm{g}}\times \frac{\mathrm{dh}}{\sqrt{\mathrm{h}}}$$$$\mathrm{v}=2\sqrt{2\mathrm{g}}(\sqrt{\mathrm{H}}-\sqrt{\mathrm{h}})$$$$\mathrm{when}\mathrm{h}=\frac{\mathrm{H}}{4}$$$$\mathrm{v}=\sqrt{2\mathrm{gH}}=\sqrt{\frac{{2\mathrm{m}}_0\mathrm{g}}{\rho \mathrm{A}}}.$$

Commented by Tinkutara last updated on 12/May/19

$$\mathrm{as}\mathrm{m}\frac{\mathrm{dv}}{\mathrm{dt}}={\mathrm{v}}_{\mathrm{rel}}\frac{\mathrm{dm}}{\mathrm{dt}}+{\mathrm{F}}_{\mathrm{ext}}$$$$PleaseexplainthisSir.$$

Commented by ajfour last updated on 12/May/19

$$\mathrm{consider}\mathrm{a}\mathrm{rocket}\mathrm{entering}\mathrm{an}$$$$\mathrm{atmosphere}\mathrm{and}\mathrm{accumulating}$$$$\mathrm{mass}\mathrm{as}\mathrm{it}\mathrm{proceeds};$$$$\mathrm{let}\mathrm{rocket}\mathrm{speed}\mathrm{be}\mathrm{v},$$$$\mathrm{External}\mathrm{force}\mathrm{acting}{\mathrm{F}}_{\mathrm{ext}}$$$$\mathrm{mass}\mathrm{dm}\mathrm{of}\mathrm{atmosphere},\mathrm{moving}$$$$\mathrm{at}\mathrm{speed}\mathrm{u},\mathrm{and}$$$$\mathrm{rocket}\mathrm{of}\mathrm{mass}\mathrm{m}\mathrm{be}\mathrm{our}\mathrm{system},$$$${\mathrm{p}}_{\mathrm{i}}=\mathrm{udm}+\mathrm{mv}$$$${\mathrm{p}}_{\mathrm{f}}=(\mathrm{m}+\mathrm{dm})(\mathrm{v}+\mathrm{dv})$$$$\mathrm{dp}=(\mathrm{v}-\mathrm{u})\mathrm{dm}+\mathrm{mdv}$$$${\mathrm{F}}_{\mathrm{ext}}\mathrm{dt}+(\mathrm{u}-\mathrm{v})\mathrm{dm}=\mathrm{mdv}$$$$\Rightarrow \frac{mdv}{dt}=v_{rel}\frac{dm}{dt}+F_{ext}.$$

Commented by Tinkutara last updated on 13/May/19

Thank you Sir!

Terms of Service

Privacy Policy

Contact: info@tinkutara.com