Question

a firecracker is fixed and rises at 1000 m find the velocity by which it was released ​

Answer 1

time taken by it to reach the highest point. Take = 9.8m/s.

1). h=1000 m

v=0 m/s ( at highest point)

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

using 3rd equation of motion

v^2=u^2+2as

0=u^2+2as

0=u^2-2*9.8*1000

-u^2=-19600

u=140m/s

2) u= 140m/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