Lucy and Kim determine the height of a building by dropping a brick from its roof. The initial velocity is 0 m/s because Lucy simply lets go of the brick. Kim times the fall of the brick to be 3.5 seconds. What is the height of the building? Also Determine the amount of time the brick is in the air if Lucy throws the brick downward with an initial velocity of -5 m/s. Round to the nearest hundredth of a second. Tysm!
2 years ago
Answered By Majid B
Dropping:
V0 = 0 m/s
a = -g = -9.81 m/s2
t = 3.5 s
d = ?
d = V0.t + (1/2).a.t2
d = (0 m/s)(3.5 s) + (0.5)(-9.81 m/s2)(3.5 s)2 = -60.1 m
Height = 60.1 m
Throwing down:
V0 = -5 m/s
a = -g = -9.81 m/s2
t = 3.5 s
d = ?
d = V0.t + (1/2).a.t2
-60.1 m = (-5 m/s)t + (0.5)(-9.81 m/s2)t2
(4.905)t2 + 5t - 60.1 = 0
t = 3.0 s