6) In the previous question, what is the velocity of the ball at the instant the

Question

6) In the previous question, what is the velocity of the ball at the instant the ball strikes the ground? a. 34.5 m/s (a 24.00 below horizontal b. 36.1 m/s (a 66.00 below horizontal c. 33.0 m/s 57.00 below horizontal d. 29.2 m/s (a 24.00 below horizontal e. 37.9 m/s (a 61.0 below horizontal ANS: B 27) A ball is thrown upward from the top of a building with an initial velocity of 28 m/s at an angle of 10 above the horizontal. If the ball strikes the ground 62.0 m from the base of the building, how tall is the building? a. 9.45 m b. 10.3 n c. 13.8 m e. 19.6 m ANS: C object over the interval 1.00s sts3.00s? a. -5.00 m/s b. 5.00 m/s c 750 m/s

Explanation / Answer

horizontal velocity = 28 cos 10 = 27.57 m/s

time in the air = 62/27.57 = 2.24 sec

vertical velocity = 28sin10 = 4.86 m/s

time to reach top point = (4.86 - 0)/9.8 = 0.49sec

so time left = 2.24-0.49 = 1.75 sec

distance dropped by ball in this time = 0.5*9.8*1.75*1.75 = 15 m

height of topmost point from top of buliding = 4.86*0.49-0.5*9.8*0.49*0.49 = 1.20 m

So height of building = 15-1.20 = 13.8 m

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