A plumb bob is hanging from the ceiling of a car. If the car moves with an acceleration a, what is the angle made by the string with the vertical?

Explanation:

Here we are assuming that the car is moving in a straight line and is traveling on a smooth surface. When the car is moving with acceleration the bob moves in the opposite direction with the same acceleration. Gravity is acting on the bob so it is experiencing an acceleration of downwards.

The angle between the acceleration and the acceleration due to gravity is

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what is the speed of a softball that travels 20m in 2secs

speed = 20/2 = 10 m/s