Changing the known formula P = M1 · V1 + M2 · V2 / M1 + M2 into the known formula of P, m, V1, V2, M2 (P ≠ V2)

Changing the known formula P = M1 · V1 + M2 · V2 / M1 + M2 into the known formula of P, m, V1, V2, M2 (P ≠ V2)

p=(m1*v1+m2*v2)/(m1+m2)
=>pm1+pm2=m1v1+m2v2
=>m2*(p-v2)=m1v1-p1m1
=>m2=(m1v1-p1m1)/(p-v2)

When an object moves in a circular motion at a constant speed, does the kinetic energy change? Does the momentum change? When the object rotates 180 degrees, how much does the kinetic energy change? How much does the momentum change?

Velocity and momentum are vectors with magnitude and direction
When an object moves in a circular motion at a constant speed, its speed and momentum change
Kinetic energy is scalar, because the velocity is constant, so kinetic energy is constant
When an object rotates 180 degrees, the kinetic energy changes by 0
If the original velocity (including direction) is V and the mass of the object is m, when the object turns 180 degrees, the velocity is (- V),
The change of momentum is Δ P = P end - P beginning = (- MV) - (MV) = - 2mV

When a particle moves in a circular motion with uniform velocity, why does the momentum change continuously while the angular momentum to the center of the circle remains unchanged?

The direction of angular momentum: angular momentum is the cross product of R (the distance vector from the reference point to the particle), which is the cross product of two vectors. In the right-hand coordinate system, it follows the right-hand spiral method, that is, the four fingers of the right hand point to the direction of R, and turn a direction less than 18