Thread: Net force on astronaut

1. Net force on astronaut

A rocket of mass 2000 tonnes, produces a constant thrust of 8x10^7N during liftoff by expelling 1500kg of exhaust gas per second.

Calculate the net force acting on an 85kg astronaut 30s after liftoff.

2. Re: Net force on astronaut

a=T-mg/m

so T is constant = 8x10^7
m=(Initial mass of the rocket + fuel system) - (mass of fuel ejected)
= 2000x1000-1500x30
= 1955000 kg

so a=T-mg/m
= 8x10^7-1955000(9.8)/1955000
= 39.9207161125 m/s^2

F=ma
= 1955000(39.9207161125)
= 3393.26086957 N

3. Re: Net force on astronaut

Originally Posted by jazz519
a=T-mg/m

so T is constant = 8x10^7
m=(Initial mass of the rocket + fuel system) - (mass of fuel ejected)
= 2000x1000-1500x30
= 1955000 kg

so a=T-mg/m
= 8x10^7-1955000(9.8)/1955000
= 39.9207161125 m/s^2

F=ma
= 1955000(39.9207161125)
= 3393.26086957 N
Thanks, that's what I thought however, the solution just used a=F/m so must have been incorrect.

4. Re: Net force on astronaut

f=ma sorry on the last bit should be 85 instead of 1955000 (used it for the end answer but forgot to change it in the typed one)

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Posting Permissions

• You may not post new threads
• You may not post replies
• You may not post attachments
• You may not edit your posts
•