Question

a ball of putty has a mass of 1.5kg and is rolling toward the north with a velocity of 2m/s. it collides with another putty ball with the same mass travelling towards the east with a velocity of 10m/s. find the velocity of the combined mass after a completely inelastic collision

Answer 1

momentum is conserved

the mass is doubled, so the velocity components are halved
... 1 m/s N and 5 m/s E

magnitude of v ... v^2 = 1^2 + 5^2

direction ... tan(Θ) = 1 / 5
... Θ is the angle north of east

Answer 2

Given:
M1 = 1.5kg, V1 = 2 m/s[90o].
M2 = 1.5kg, V2 = 10 m/s[0o].
V3 = Velocity of M1 and M2 after collision.

Momentum before = Momentum after.
M1*V1 + M2*V2 = M1*V3 + M2*V3.
1.5*2i + 1.5*10 = 1.5V3 + 1.5V3,
15 + 3i = 3V3,
V3 = 5 + 1i = 5.1m/s[11.3o].