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  • A ball is thrown from a roof top at an angle of 45^{o} above the horizontal. It hits the ground a few seconds later. At what point during its motion, does the ball have a) greatest speed b) smallest speed c) greatest acceleration?

A ball is thrown from a roof top at an angle of 45^{o} above the horizontal. It hits the ground a few seconds later. At what point during its motion, does the ball have

a) greatest speed

b) smallest speed

c) greatest acceleration?

Answers (1)

The ball is thrown from point O. The angle with the horizontal is 45 degree. As the height increases from O to A, the speed decreases. At B, the speed becomes equal to its initial speed. The height decreases further from B to C and becomes maximum at point C.

V_{x}=u\; \cos 45=\frac{u}{\sqrt{2}}\; m/s

a) greatest speed of the ball is at c as V_{y} and V_{x}=u\; \cos\; 45=\frac{u}{\sqrt{2}}\; m/s

b) slowest speed will be at point A. here V_{y}=0, and the horizontal speed is V_{x}=\frac{u}{\sqrt{2}}

c) the greatest acceleration will be the one caused by the gravitational force downward, which will be equal to g.

 

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infoexpert24

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