Question

A fire cracker is fired and it rises to a height of 1000 m. Find the velocity by which it was released and Time taken by it to reach the highest point. (Take g =9.8 m/s )​

Answer 1

Answer:

(1) h=1000m

     v= 0 m/s (at highest point)

      g= 9.8 m/s( taken to be negative according to sign convention)

     

Using 3rd equat. of motion,

v^2= u^2 + 2as

0 = u^2- 2*9.8*1000

-u^2= -19600

u^2= 19600

u=140 m/s

(2) u=140 m/s (as calculated above)

  1st equation of motion,

v= u+at

0=140+(-9.8)t

-140= -9.8t

140= 9.8t

t=  1400/98

t=  14.3 seconds

t= 14 seconds( approximately

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