An object falls with an acceleration of a= -9.81 m/s^2. A function relating the height from which the object falls, the initial velocity of the object, and the time the object spends in the air is frequently used in physics. 

 

Lucy and Kim determine the height of a building by dropping a brick from its roof. The initial velocity is 0m/s because lucy simply let go of the brick. Kim times the fall of the brick to be 3.5 seconds. What is the height of the building? 

 

Determine the amount of time the brick is in the air if Lucy throws the brick downward with an initial velocity of -5m/s. Round to the nearest hundreth of a second. 

3 years ago

Answered By Mahboubeh D

y= $\frac{1}{2}$12  gt²+V₀t+y₀

₀₌ $\frac{1}{2}$12  (-9.81)(3.5)²+y₀

H=y₀=60.08 (m)

y= $\frac{1}{2}$12  gt²+V₀t+y₀

0= $\frac{1}{2}$12  (-9.81)t²-5t+60.08

t=3.02(s)$\approx$≈3(s) 

 

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