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A ball is thrown horizontally from the top of a building 37.5 m high. The ball strikes the ground at a point 80.3 m from the base of the building. The acceleration of gravity is 9.8 m/s 2 . Find the time the ball is in motion. Answer in units of s.

User Ctomek
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1 Answer

4 votes

Answer:

t = 2.77 s

Step-by-step explanation:

The ball in its movement describes a curved line called a semiparabola, therefore two coordinates are required to fix the position at each instant of time, since the movement is performed in the X-Y plane:

Equation of movement of the ball in the X axis

X = v₀x*t Equation (1)

Equation of movement of the ball in the Y axis

Y = y₀+ v₀y*t -½ g*t² Equation (2)

Where

X : horizontal position in meters (m)

Y : vertical position in meters (m)

y₀ : initial vertical position in meters (m)

v₀x : X-initial speed in m/s

v₀y : Y-initial speed in m/s

g: acceleration due to gravity in m/s²

t : time to position (X,Y)

Data

y₀ = 37.5 m

v₀y = 0

g = 9.8 m/s²

Problem development

The time the ball remains in the air is the same as the ball takes to touch the floor, that is, Y = 0

We apply the Equation (2):

Y = y₀+ (v₀y)*t - (½) g*t²

0 = 37.5 +(0)*t- (1/2)*(g)*t²

0 = 37.5 - (1/2)*(9.8)*t²

(1/2)*(9.8)*t² = 37.5

t² = (2)(37.5)/(9.8)


t= \sqrt{(2*37.5)/(9.8) }

t = 2.77 s

User Lucas Fabre
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