A food packet is released from a helicopter rising steadily at the speed of 2ms-1. What is velocity of packet after 2sec?

1 )  A food packet is released from a helicopter rising steadily at the speed of 2ms-1. What is velocity of packet after 2sec?

Solution:-   (i)  Velocity of packet:-     

Given data:-    

1):-  vi = 2 m/s  ( initial velocity of packet will become same as velocity of helicopter moving).  ,        

2):- t = 2s ,         ( time as given)

3):- g = a = -10 m/s (Because as we know that value of "a" while coming downward is (-ve)  and value of "a" while going upward is (+ve)).

Must remember this:-

Soln:-

               vf=vi+at  ............(first equation of motion).

               vf=  2+(-10)(2) = 2 + (-20)

               vf = -18 m/s.

   (-ve) sign shows that packet is coming downward and here we used simple formula because time and initial velocity is given . 

   (ii)  how far packet is from helicopter after 2 mintues:-

    (a):-  So first we calculate the total distance covered by helicopter,

                  Distance coverd by helicopter: d= v*t 

                                                                    d=2*2= 4m .    (Here we simply use velocity-distance formula because helicopter is going in  (x-axis) horizontal direction . so as we also know that in x-asis , acceleration is zero.) 

     (b):-  Distance coverd by packet : S =(vf² - vi² )/2g

                                                             S = ((-18)² - (2)²)/2(10) 

                                                             S = ( 324 - 4)/20  =  320/20

                                                             S = 16m.

Here we used 3rd equation of motion  (2gS =vf² - vi² ) , because packet is going downward and we have to add value g also.

Total Distance between packet and helicopter:-

So total distance = D = d+S 

                               D= 4+16 

                               D = 20m.   Answer .

3 )  Different radioactive materials have  ......................... ,

A ) Different half life ,                       B ) same total life ,

C ) Both of these ,                                                D ) None of these ,

Correct Answer : - C ) Both of these ,

4 )  From Laplace correction , the propagation of sound in gas is ........................ ,

A ) adiabatic process ,                                B ) Isothermic process ,

C ) Both of these ,                                                D ) None of these ,

Correct Answer : - A ) adiabatic process ,    

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