9) Kaitlynn fired a projectile at time t=0.0 s, from the edge of a cliff (y=0),

Question

9) Kaitlynn fired a projectile at time t=0.0 s, from the edge of a cliff (y=0), with initial velocity of vo=200 m/s and initial angle of 30 degree above the horizontal. The projectile rises, and then falls into the sea at point P. the time of flight of the projectile is 45.0 s. In the figure, the y-coordinate of the projectile velocity when its x-coordinate is 1000 m is closest to: 11) In a football field, Kyle is attempting a field goal from 34 m out. The ball is kicked and just clears the lower bar. The time to reach maximum height is 1.6s. If the angle of the kick was 35 degree, What was the initial speed of the ball?

Explanation / Answer

Number 9)

In the x direction, the velocity will always be the same

We can find the time to fly 1000 m horizontally.

d = vt

1000 = (200)(cos 30)(t)

t = 5.77 sec

Then in the y direction

d = vot + .5at2

d = (200)(sin 30)(5.77) + (.5)(-9.8)(5.77)2

d = 414 m

That is choice C with rounding (410 m)

Number 11)

At the max height the y velocity goes to zero..

Apply vf = vo + at

0 = voy + (-9.8)(1.6)

voy = 15.68 m/s

That is the y component, so the actual velocity = 15.68/(sin 35)

v = 27.3 m/s

That is choice C

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