Achild of mass 25 kg is skating fast, +10 m/s, and tries to get revenge by colliding with the 60 kg adult who is sitting still. after the collision, the adult goes forward at 6 m/s. what is the child's final velocity?

-4.4 m/s

Explanation:

This problem can be solved by the Conservation of Momentum principle, which establishes that the initial momentum must be equal to the final momentum :

(1)

Where:

(2)

(3)

is the mass of the child

is the initial velocity of the child

is the mass of the adult

is the initial velocity of the adult (it is sitting still)

is the final velocity of the child

is the final velocity of the adult

Substituting (2) and (3) in (1):

(4)

Isolating :

(5)

(6)

Finally:

This means the velocity of the child is in the opposite direction

the temperature in kelvin of 2.0 dm3 of an ideal gas is doubled and its pressure is increased by a factor of four. what is the final volume of the gas