No additional force is required because it's already going downhill
It changes the motion as Newton's second law of motion states that a force, acting on an object, will change its velocity by changing either its speed or its direction or both. If your basketball goes rolling into the street and is hit by a bike, either the ball will change direction or its speed or both.
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speed of light waves change when they travel in air to aquarium because want's the light hits the water you see bunches of color along with bigger looking objects
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