Two hockey players are traveling at velocities of v1 = 10 m/s and v2 = -22 m/s when they undergo a head-on collision. after the collision, they grab each other and slide away together with a velocity of -3.6 m/s. hockey player 1 has a mass of 123 kg. what is the mass of the other player?

The negative sign in the velocity simply indicate direction, nothing else. From the conservation of momentum, we have the equation:

m1 v1 + m2 v2 = (m1 + m2) v’

 

123 kg (10 m/s) + m2 (-22 m/s) = (123 kg + m2) (-3.6 m/s)

1230 – 22 m2 = -442.8 – 3.6 m2

18.4 m2 = 1672.8

m2 = 90.91 kg

Neptune is the eighth planet from the sun. it was the first planet to get its existence predicted by  mathematical calculations  before it was actually seen through a telescope on sept. 23, 1846. irregularities in the orbit of  uranus  led french astronomer alexis bouvard to suggest that the gravitational pull from another celestial body might be responsible. german astronomer johann galle then relied on subsequent calculations to   spot neptune via telescope. previously, astronomer galileo galilei sketched the planet, but he mistook it for a star due to its slow motion. in accordance with all the other planets seen in the sky, this new world was given a name from greek and roman mythology — neptune, the roman god of the sea.