A ball is thrown straight upward with an initial velocity of 8 m/s. the magnitude of the final velocity of the ball is A. 0 m/s
B. 4 m/s
C. 8 m/s
D. 16 m/s

Assuming no air restance the speed when the ball comes back to the starting point will be again 8ms but directed DOWNWARDS; we can express this by saying that it will equal to −8ms adding a minus to indicate the downward direction.

To find the time of flight we use:

vf=vi+at

Where:

a is the acceleration of gravity (downwards, −9.8ms2);

vi=+8ms

vf=−8ms

So, we get:

−8=8−9.8t

−16=−9.8t

t=169.8≈1.6s

The answer is "B"

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the total distance traveled by the car is

30km + 49km = 79 km .