If an object is moving at a constant speed in one direction, what is needed to change its speed or direction? a. a balanced force b. an unbalanced force c. a long period of time d. a short period of time

To change the speed or direction of the object's motion requires one or more forces that don't add up to zero.

An unbalanced force, the net force can't be equal or the object would stay in rest.

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.

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