A person, on top of an 80m tall building, throws a book at a downward 60circ ang

Question

A person, on top of an 80m tall building, throws a book at a downward 60circ angle. The book is in the air for 3s before hitting the ground. (Ignore air resistance.)

a.) Determine the initial speed with which the book is thrown.

b.) Determine how far (horizontally) the book is from the building at 3s.

A kicker must kick a ball from a point 36m from the goal post. The ball must clear
a crossbar which is 3:05m high. The kicked ball leaves the ground with a speed of
20m=s at an angle of 53.
a.) Does the ball clear the crossbar or come short?
b.) By how much?
c.) Does the ball approach the crossbar while still rising or while falling?

A baseball is hit from a height 1m from the ground. The ball is observed to reach
its maximum height above the ground 3:0s after being hit. 2:5s later the ball is
observed to hit the very top of a fence that is 100m away. How tall is the fence?

Explanation / Answer

GIVEN THAT

h = 80 m

theta = 80 deg

time of flight is T = 3 sec

using kinematic equation

h= (Vo*sin(60)*T)+(0.5*g*T^2)

80 = (Vo*sin(60)*3)+(0.5*9.8*3^2)

(Vo*2.6)+(44.1) = 80

2.6*Vo = 80-44.1 = 35.9

Vo = 35.9/2.6 = 13.8 m/sec

b) Horizontal distance travelled is H = Vo*cos(60)*T = 13.8*cos(60)*3 = 20.7 m

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