A man dropped a ball vertically downward from a top of 170m building?

Question

a man dropped a ball vertically downward from a top of 170m building.

a. find the total time of flight

b. find the maximum velocity of the ball

c. if it is 3/4 of the height of the building find the velocity it has.

d. what is the position of the ball after 3 sec. it was accidentally fell?

e. how much time elapsed when it traveled 1/2 of the height of the building?

with solution please.... thanks.. XOXOXo

Answer 1

A) s = 1/2 * a * t^2

170 = 1/2 * 9.81 * t^2

170 / (1/2 * 9.81) = t^2 = 34.659

t = 5.89 seconds

B) v = u + at

v = 0 + 9.81 * 5.89 = 57.78 ms^-1

C) 170 * 3/4 = 127.5

170 - 127.5 = 42.5 metres travelled.

42.5 = 1/2 * 9.81 * t^2

t = 2.94 seconds

v = 0 + 9.81 * 2.94 = 28.84 ms^-1

D) s = 1/2 * a * t^2

s = 1/2 * 9.81 * 3^2 = 44.145 metres below the top of the building. i.e. 170 - 44.145 = 125.86 metres high.

E) s = 85

85 = 1/2 * a * t^2

85 = 1/2 * 9.81 * t^2

85 / (1/2 * 9.81) = t^2 = 17.33

t = 4.163 seconds