Question

A rocket, initially at rest on the ground, accelerates straight upward from rest with constant acceleration 58.8 m/2^2. The acceleration period lasts for time 8.00 S, until the fuel is exhausted. After that, the rocket is in free fall.
Find the maximum height Vmax reached by the rocket. Ignore air resistance and assume a constant acceleration due to gravity equal to 9.80 m/s^2 .

Answer 1

*58.8 m/s^2

Answer 2

i found the height when the fuel is exhausted which is = to 1880

Answer 3

the velocity at that point i think is 470 m/s

Answer 4

i think i have to find the distance it went after that and add it?

Answer 5

yep

Answer 6

that 1880, how did you come to that

Answer 7

1881.6 lol

Answer 8

yea rounded wrong LOL

Answer 9

470.4 m/s correct

Answer 10

I must complain about this question - it doesn't take into account the loss of mass as the fuel is ejected.

Answer 11

yea physics is a pain.. LOL

Answer 12

hey man it's simple physics lol. if you take mass into account, school students are doomed

Answer 13

i was using this formula Xf=Xi+(Vx)i Dt + 1/2Ax(Dt)^2

Answer 14

when ever i see a physics problems i get anxiety.. =(

Answer 15

ttt luv the pic

Answer 16

anyway, what's the distance traveled after fuel ran out?

Answer 17

i couldnt figure it out

Answer 18

im thinking i have to use this formula
V^2 = Vo^2+2a(y-yo)
Vo is the initial velocity which is 470 m/s?

Answer 19

ok, take upwards as possitive direction at the point where feul ran out, u=470.6m/s, a=-9.8m/s^2m, v=0m/s at max point.
use v^2=u^2+2aS

Answer 20

a=-9.8m/s^2 negative since acceleration downwards. gravity

Answer 21

uh huh!

Answer 22

so plug them in the equation, you'll find distance from no more gas point to max point, add this to distance from ground to ran out point to get max height

Answer 23

what do i plug in for S?

Answer 24

that's what you need to find. plug everything in to find S

Answer 25

0=470.6^2 + 2 (-9.8)S

Answer 26

yeap

Answer 27

11299

Answer 28

yea, looks reasonable
add this S to the S before(1881.6) you get max height

Answer 29

damn man youre a genius!

Answer 30

it took me an hour to figure out the first part =(

Answer 31

don t worry you will get used to it very soon, just keep practicing. All those problems more or less are the same

Answer 32

thanks! when can i buy you lunch!? LOL

Answer 33

lol what do you think, I eat physics for lunch hahaha. just kidding. I'm off to bed now. see ya.

Answer 34

haha thanks good night!