please help me work out these physics questions...:)

rockets fail when you are 110m above moon surface. speed of descent is 4.5m/s. without rockets speed will increase by 1m/s every sec
1) Show that you'll travel 5m in 1st sec after rocket fails and 6m in 2nd etc
2) how long will it take from 110m up to hit moon floor
3) what speed will you hit moon

force= mass x speed of impact/time taken to stop

lunar module has 4 legs- each meets surface at same time.
4) total mass 700kg + impact 0.1s what is force on each leg?

could any1 plz show me how they worked these out as i am confused... :confused:

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Reply 1

chr15chr15

1) use suvat s = ut + 0.5at^2
2) use suvat same equation
3) you want v any equation with v in will work
4) you have the formula in front of you shouldn't need help on this but anyways
you have mass you worked out speed in 3) and it takes 0.1s to stop you can then work out total force
and divide it by 4 for each leg!

Reply 2

panjabiflower

'use suvat s = ut + 0.5at^2'
could you please explain this equation to me and what the letters symbolise as i have only started AS physics today thank you :smile:

Reply 3

chr15chr15

panjabiflower

'use suvat s = ut + 0.5at^2'
could you please explain this equation to me and what the letters symbolise as i have only started AS physics today thank you :smile:

ok if you stated that in the first post i would have provided more help! :biggrin:

s = displacement just think of it as distance for the moment.
u = initial speed in this case it was 4.5m/s i think
t = time
a = acceleration which is 1s

Reply 4

panjabiflower

hi i used the equation to help give me 5m in Q1 but i can't get 6metres for 2 seconds

Reply 5

chr15chr15

panjabiflower

hi i used the equation to help give me 5m in Q1 but i can't get 6metres for 2 seconds

did you get 11 by any chance?

btw is the answer to q2 66s

Reply 8

chr15chr15

panjabiflower

you travelled 5 in the first second
you travelled 11 in the first 2 seconds

so in the 2nd second you travelled 11 - 5 = 6s
:smile:

Reply 9

chr15chr15

panjabiflower

btw is the answer to q2 66s

i got 11 seconds!

Reply 10

panjabiflower

i got 1/2t^2+4.5t-110=0 what do i do now?

Reply 11

panjabiflower

chr15chr15

i got 11 seconds!

how did you get this?

Reply 12

chr15chr15

panjabiflower

i got 1/2t^2+4.5t-110=0 what do i do now?

well to make it look nicer i divided everything by 0.5
giving:
t^2 + 9t -220 = 0

now you have to put it into 2 brackets and what would you know 11 and 20 fit very nicely!