Use the worked example above to help you solve this problem. A ball is thrown up

Question

Use the worked example above to help you solve this problem. A ball is thrown upward from the top of a building at an angle of 30.0 degree to the horizontal and with an initial speed of 18.0 m/s. The point of release is h = 42.0 m above the ground. How long does it take for the ball to hit the ground? Find the ball's speed at impact. Find the horizontal range of the ball. Suppose the ball Is thrown from the same height as in the PRACTICE IT problem at an angle of 25.0 degree below the horizontal. If It strikes the ground 59.3 m away, find the following. the time of flight the Initial speed the speed and angle of the velocity vector with respect to the horizontal at impact

Explanation / Answer

a)

the time is calculated as follows:

h = v0sin@*t - 0.5gt2

-42 = 18*sin30* t - 0.5*9.8*t2

  -42 = 9 t - 4.9*t2

after solving, we get, t = 3.98 s

b)

the horizontal speed is,

v0x = v0cos@ = 18cos30 = 15.588 m/s

the verticla velocity is,

v0y = v0sin@ = 18sin30 = 9 m/s

the final vertical speed is,

vy = v0y - gt = 9 - 9.8*3.98 = -30.004 m/s

thus, the fianl speed is,

v = sqrt[vx2+vy2] = 31.32 m/s

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the horizontal range is,

R = v02sin2@/g = 28.6 m

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