Calculate Rocket Thrust Force of 90g Rocket Achieving 80m/s in 3.0s

[Sucks@Physics]

A toy rocket, of mass 90g, acheives a velocity of 80m/s after 3.0s when fired straight up. What average thrust force does the rocket engine exert?

I dont' know what formula to use for this

 

[hage567]

Can you find the average acceleration?

 

[aq1q]

is this held in Earth where gravity exists? lol, i know its a dumb question, but sometimes during my life, i have done problems like these without the involvement of gravity.

 

[Sucks@Physics]

avg acceleration = 26.667m/s and lol yea its on earth

 

[Sucks@Physics]

no help?

 

[hage567]

avg acceleration = 26.667m/s and lol yea its on earth

Acceleration is in m/s^2.

So what's Newton's second law?

 

[Sucks@Physics]

what i did is...

Fnet = (m*v)/t

Fnet = (.09*80)/3 = 2.4N

What did i do wrong?

 

[Sucks@Physics]

Am i not supposed to be solving for Fnet?

 

[Sucks@Physics]

Can some1 help i ahve to have this finished by tomorrow and I'm doing it wrong

 

[Feldoh]

Does it give you a rate at which the mass of the rocket is changing?

 

[Sucks@Physics]

I think I'm neglecting that.

 

[aq1q]

ok, start out by drawing a free-body diagram. since the thrust is accelerating upwards.. thrust must me greater than weight. therefore Ft-W=Ma soo Ft=w+ma, right?

Solve for a, and then just plug and chug..

 

[Sucks@Physics]

sweet thanks, i get it now

 

[physicnoob101]

ok, start out by drawing a free-body diagram. since the thrust is accelerating upwards.. thrust must me greater than weight. therefore Ft-W=Ma soo Ft=w+ma, right?

Solve for a, and then just plug and chug..

hey, i have the same question, but what does w stand for? since m = mass, Ft = force of thrust anf a = acceleration (right)? then what is w?

 

[SteamKing]

What force must the rocket thrust counteract in order for the rocket to rise?