InterviewSolution
Saved Bookmarks
InterviewSolution
| 1. |
It is common observation that rain clouds can be at about a kilometre altitude above the grond. (a) If a rain drop falls from such a height freely under gravity, what will be its speed ? Also calculate in km //h. (g=10 m//s^2) (b) A typical rain drop is about4 mm diameter. Vomentum is mass xxspeed in vagnitude . Estimate its momentum when it hits ground. (c ) Estimate the time required to flatten the drop. (d) Rete of change of momentum id force. Fstmate how much forece such a drop would exert you. (e) Estiate the order of magitude force of magnitude force on umbrella.Typical lateral separation between tao rain drops is5 cm. (Assume that umbrella is circular and has a diameter of1 m and cloth is not prierced through it) |
| Answer» <html><body><p></p>Solution :Here, ` <a href="https://interviewquestions.tuteehub.com/tag/h-1014193" style="font-weight:bold;" target="_blank" title="Click to know more about H">H</a>= 1000 m, g=10 m//s^2` <br/> (a) Velcoity of rain drop after fallin height (h) si <br/> ` v = sqrt (2 gh) = sqrt (2 xx 10 xx 1000) = 100 sqrt 2 m//s = ( 100 sqer 2 xx 60 xx 60)/(1000) km// h = 36 0 sqrt 2~~ 510 km //h` <br/> (<a href="https://interviewquestions.tuteehub.com/tag/b-387190" style="font-weight:bold;" target="_blank" title="Click to know more about B">B</a>) Diameter of drop, ` d = 2 =4 mm or r= 2 mm = 2 xxx 10^(-3)m` <br/> Mass of rain drop, ` m= 4/3/ pi r^3 roh = 4/3 xx (220/7 xx ( 2 xx 10^3)^3 xx 10^(-3)^3 xx 10^3 ~~ 3.4 xx 10 ^(-5) kg` <br/> Mumentum of rain drop when it hits the ground, ` P = mu = ( 3.4 xx 10 ^(-5) xx 100 sqrt 2 ~~ 4.7 xx 10^(-3) kg m//s` <br/> (c ) Timerequired to flatten the frop is <br/> ` <a href="https://interviewquestions.tuteehub.com/tag/delta-947703" style="font-weight:bold;" target="_blank" title="Click to know more about DELTA">DELTA</a> t = d/v = (4 xx 10^(-3))/(100 sqrt 2) = 0/028 xx 10^(-3) = 28 xx 10^(-6) s` <br/> (d) Force, ` F= (change in momentum )/(time) = ( P-0)/(Delta t) = ( 4. 7 xx 10^(-3))/(28 xx 10^(-6)) ~~ 16 <a href="https://interviewquestions.tuteehub.com/tag/8-336412" style="font-weight:bold;" target="_blank" title="Click to know more about 8">8</a> N` <br/> (e) Given , rakies of umbrella, ` R = 1//2 m` <br/> Area of umbrella ` =pi R^2 = 922) /7 9 1/2 )^2 = (22)/(28) = (11)/(14) ~~ 0.8 m^@` <br/> with average separaion of ` 5 cm (= 5 xx 10^(-2) m), number of drops those will hit nubrella simultanceously <br/> ` = (0.8)/((5 xx 10^(-2))^2` <br/> Net force on umbrella`= 320 xx 168 = 53760 N ~~ 54000 N`.</body></html> | |