A0.16 kg billiard ball moving at 1.20 m/s collides elastically with one of the same mass at rest. it continues at a speed of 0.6 m/s afterward in a different direction from before. what is the final speed of the other billiard ball?
i thought it was .6 m/s because it is elastic, but it says i am wrong.

Use energy conservation to calculate the speed!
Total kinetic energy before collision = total kinetic energy after the collision.

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.

The best description is: . nobody has any idea what q is.