IIT JEE , AIEEE Forum - Physics , General

sam26kal

a rocket is fixed vertically up frm d ground, with resultant vertical acc 10 m/s^2. the fuel is finished in 1 min& it continues 2 move up

(a) wats d max height reached

(b)after how much time from then will the maximum height be reached

(c) with wat velocitty will it hit the ground ( g = 10 m/s^2)

raman_shadow

firstly use s = ut + 1/2 at²

now s = 0 + 5(60)² {time is 1 min and resultant acc. is 10}
s = 18000 m

also using v = u + at
v = 0 + 600 = 600 m/s
now after this pt the fuel is completely used and net g acts on body

so using v² - u² = -2gh
0 - 360000 = -20h
h = 18000 m

so max ht reached = s + h = 18000 + 18000 = 36000m = 36 km

now using v = u - gt after fuel is used up
0 = 600 - 10t
t = 60s
so total time till max ht is 60 + 60 = 120s = 2min

now using v² - u² = 2gh during free fall motion

v² - 0 = 20 x 36000

v² = 720000
v = 600

2 m/s

so it falls on ground with this vel.

pls rate if crrect..........

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