A50-kg ice skater is holding a 3-kg ball, moving at a steady +5 m/s. she then throws the ball backwards
at -10 m/s, if so what would her final velocity be?

5.9 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 skater

is the mass of the ball

is the initial velocity of the skater and the ball

is the final velocity of the ball

is the final velocity of the skater

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

(4)

Isolating :

(5)

(6)

Finally:

i am pretty sure it is c because when people are closer together, they cannot move as freely. picture being in a mostly full elevator, for instance. the people are right next to you, and you can barely move.