Problem 2 Tennis ball machines can throw balls with a speed of 26.8 m/s. Somebod

Question

Problem 2

Tennis ball machines can throw balls with a speed of 26.8 m/s. Somebody thought it would be a good idea to take one of these machines to the top of a building and fire balls off, to drop on the unsuspecting people below. The machine is 80.0 m above the ground, firing balls horizontally off the top of the building. (please write out the problems on a sheet of paper and be sure handwriting is clear)

a) How long does it take for one of the fired balls to hit the ground?

b) What is the horizontal (x) component of the velocity when it hits the ground?

c) What is the vertical (y) component of the velocity when it hits the ground?

d) If someone just picked up a tennis ball and dropped it from the top of the building (without throwing it sideways), what would be the dropped ball’s velocity (x and y components)?

Explanation / Answer

(A) ball are thrown horizontally so initial vertical velocity.

v0y = 0

vertical displacement = 0 - 80 m = - 80 m

Applying y = v0y t + ay t^2 /2

-80 = 0 - 9.8 t^2 /2

t = 4.04 sec

(B) there is no force or acceleration in horizontal hence horizontal component will not change.

v0x = 26.8 m/s

(c) vy = v0y + a t

vy = 0 - 9.8 x 4.04 = - 39.6 m/s

(d) vfx = 0

and vfy = - 39.6 m/s

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