A2kg mass is moving on a frictionless airtrack. it collides into a motionless 1.5 kg mass.
what is the combined speed of the two masses if they stick together on impact

Explanation:

From the law of conservation of momentum, the sum of initial momentum equals the sum of final momentum

Momentum, p=mv where m is the mass and v is the velocity

where is the common velocity, and are velocities of 2 Kg moving mass and motionless 1.5 kg mass respectively, and are masses of 2 Kg moving mass and motionless 1.5 kg mass .

Since the 1.5 Kg mass is motionless, it's velocity is zero hence

By substitution

1/0.14nm = 10^10/1.4 a lot