HELPConservation of momentum lab

[pie877]

1. we did a lab putting baking soda, citric acid, and water into a film canister and we had to find the amount of each ingrediant to give the max height when propelled by material, and once we have that we time it and the questions is to find the velocityof the canister when the propellant erupts
m (of canister) 4.1g
m (of baking soda, citric acid and water) 7g
m (of water) 10 ml (10 g)
time (from liftoff to landing) 1.29 s
max height 6m

Homework Equations

we know the basic kinematics equations such as:
d=v1t+1/2at^2
v2^2=v1^2 + 2ad

also we know conservation of momentum equation
p1=p2
m1v1+m2v1+m3v3=m1v'1+m2v'2+m3v'3



3. The Attempt at a Solution
i tried using the 1st equation d=v1t+1/2at^2 but my speed was 12.6
when t=.645s (time to reach max height) and a=9.8m/s^2 and d=6 m (max height)
but I am not sure if we need to use the momentum equation? and how t go about to this lab?

 

[tiny-tim]

welcome to pf!

hi pie877! welcome to pf!

(try using the X² and X₂ icons just above the Reply box )

i tried using the 1st equation d=v1t+1/2at^2 but my speed was 12.6
when t=.645s (time to reach max height) and a=9.8m/s^2 and d=6 m (max height)
but I am not sure if we need to use the momentum equation?

no, energy will do …

either use KE + PE = constant,

or use one the standard constant acceleration equations (not d = v₁t + 1/2at², it has too many unknowns, use one with v₂ in … I'm assuming the canister is going straight up )

 

[I like Serena]

Hi pie877, welcome to PF :)

(Please refrain from using bold face - it hurts my eyes!)

time (from liftoff to landing) 1.29 s
max height 6m

The Attempt at a Solution

i tried using the 1st equation d=v1t+1/2at^2 but my speed was 12.6
when t=.645s (time to reach max height) and a=9.8m/s^2 and d=6 m (max height)
but I am not sure if we need to use the momentum equation? and how t go about to this lab?

Can you explain how you found a speed of 12.6 when t=.645s?

Btw, the momentum equation is not of use in this case.

 

[pie877]

Alright I'll try that and yes it's going straight up
Thx

 

[pie877]

either use KE + PE = constant,

or use one the standard constant acceleration equations (not d = v₁t + 1/2at², it has too many unknowns, use one with v₂ in … I'm assuming the canister is going straight up )

should i get the same answer tho?

cuz I am not sure which mass to use for KE+PE=constant
like mass of canister or mass of canister and contents lol

 

[tiny-tim]

hi pie877!

(just got up :zzz: …)

cuz I am not sure which mass to use for KE+PE=constant
like mass of canister or mass of canister and contents lol

use the mass of whatever goes up …

any contents that get left behind don't count ​

 

[pie877]

Thanks I got it to work lol :)