Explosion of firecracker on pond

[omc1]

Homework Statement

A firecracker (mtot = 0.70 kg), sitting on a frozen pond, explodes into three pieces, each of which moves horizontally. Piece 1 (m1 = 0.20 kg; v1 = 100 m/s) moves at a right angle to piece 2 (m2 = 0.20 kg; v2 = 125 m/s). What is the speed of the third piece?

Homework Equations

mv=p=j=ft

The Attempt at a Solution

m(tot)v1+v2+v3=ft i think t=v(final)/a and a would be equal to gravity but iam just not sure. thanks for help!

 

[tiny-tim]

hi omc1!

A firecracker (mtot = 0.70 kg), sitting on a frozen pond, explodes into three pieces, each of which moves horizontally. Piece 1 (m1 = 0.20 kg; v1 = 100 m/s) moves at a right angle to piece 2 (m2 = 0.20 kg; v2 = 125 m/s). What is the speed of the third piece?
…
m(tot)v1+v2+v3=ft

what is this supposed to be?

what principle do you think applies here?

(and what topics have you been lectured about this week?)​

 

[omc1]

we have only talked bout impulsion and momentum so far i think thurseday we begin collision...

 

[omc1]

the formula applies to mas total times the sum of the velocities is the force times time...

 

[tiny-tim]

we have only talked bout impulsion and momentum so far i think thurseday we begin collision...

an explosion is a type of collision (in reverse!)

what happens to momentum in a collision?

(and do you need to answer this before thursday?!)

 

[omc1]

momentum is conserved in a collision, yes my homework is due wednesday night.

 

[tiny-tim]

momentum is conserved in a collision

ok, the initial momentum is zero

(because the question says the firecracker is "sitting")

sooo …​

 

[omc1]

mmmm ok so m(tot)v1+v2+v3=0 iam not sure

 

[tiny-tim]

mmmm ok so m(tot)v1+v2+v3=0 iam not sure

no, that's multiplying the total mass by the sum of the velocities

you need to add the individual momentums (ie individual mass times individual velocity)

 

[omc1]

soo m1v1+m2v2+m3v3=0 ??

 

[tiny-tim]

yup!