two ice skaters stand facing each other. Melissa who weighs 58kg pushes off of brandon who weighs 78kg. If melissa moves backwards at a velocity of 2.1 m/s, what is Brandons final velocity? (i know u use M1V1=M2V2)

Question

shamim · Answer

do u know conservation of momentum

shamim · Answer

m1.u1+m2.u2=m1.v1+m2.v2

shamim · Answer

so total  momentum before pushing =total momentum after pushing

shamim · Answer

u know
u1=0
u2=0

festinger · Answer

The conservation of momentum states that the total momentum before and after is the same. That is to say $$m_{melissa}v_{i, melissa}+m_{brandon}v_{i,brandon}=m_{melissa}v_{f, melissa}+m_{brandon}v_{f,brandon}$$where $m$ is for mass and $v$ is velocity. The indices $i$ and $f$ stand for initial and final respectively. Now, from the problem statement, initially both skaters are stationary, that is, $v_{i,melissa}=v_{i,brandon}=0$, so the conservation of momentum equation is now: $$0=m_{melissa}v_{f, melissa}+m_{brandon}v_{f,brandon}$$
If you substitute $m_{melissa}=58$, $v_{f, melissa}=2.1$ amd $m_{brandon}=78$, ypi can solve for $v_{f, brandon}$. Note that the minus sign that arises because brandon must move in the opposite direction.