A home run is hit in such a way that the baseball just clears a wall 12 m high,
ID: 1869271 • Letter: A
Question
A home run is hit in such a way that the baseball just clears a wall 12 m high, located 116 m from home plate. The ball is hit at an angle of 33° to the horizontal, and air resistance is negligible. (Assume that the ball is hit at a height of 1.0 m above the ground.) (a) Find the initial speed of the ball. m/s b) Find the time it takes the ball to reach the wall. (c) Find the velocity components of the ball when it reaches the wall. x-component m/ y-component Find the speed of the ball when it reaches the wall. m/s m/sExplanation / Answer
a)
consider the motion along the X-direction
Vox = initial velocity = vo Cos33
X = horizontal displacement = 116
t = time of travel = ?
using the equation
X = Vox t
116 = (vo Cos33) t
t = 116 /(vo Cos33) eq-1
consider the motion along the Y-direction
Voy = initial velocity = vo Sin33
a = acceleration = - 9.8
Yo = initial Position = 1 m
Yf = final Position = 12 m
using the equation
Y = Yo + Voy t + (0.5) a t2
12 = 1 + (vo Sin33) (116 /(vo Cos33)) + (0.5) (- 9.8) (116 /(vo Cos33))2
vo = 38.2 m/s
b)
using eq-1
t = 116 /(vo Cos33)
t = 116 /((38.2) Cos33)
t = 3.62 sec
c)
Along the X-direction , final velocity as it reach the wall is given as
Vfx = Vox = vo Cos33 = (38.2) Cos33 = 32.03 m/s
Along the Y-direction , final velocity as it reach the wall is given as
Vfy = Voy + at
Vfy = (38.2 Sin33) + (- 9.8) (3.62)
Vfy = - 14.7 m/s
d)
speed at the wall is given as
Vf = sqrt(Vfx2 + Vfy2) = sqrt((32.03)2 + (- 14.7)2) = 35.2 m/s
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