Question

A firecracker is fired and it rise to a 1000 m find it
(1) velocity bye which find the velocity by which it was which it was raised
(2)time taken by light to reach the
3
highest point Gravity=9•8S

Answer 1

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.



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