A projectile is fired from the ground (you can assume the initial height is the
ID: 1525872 • Letter: A
Question
A projectile is fired from the ground (you can assume the initial height is the same as the ground) in a field so there are no obstacles in its way. It is fired at an angle 34° with respect to the horizontal and with an initial speed of 25 m/s. Air resistance is negligible in this situation.
1-What is the maximum height that the projectile reaches?
2-What is the speed of the projectile at its maximum height?
3-The same projectile was then fired in the same way toward a wall that is a horizontal distance 49.6 m from where the projectile was fired.
What was the height of the projectile when it hit the wall?
4-What was the velocity of the projectile when it hit the wall?
Call down the positive y direction, and toward the wall the positive x direction. ...i+..j
Explanation / Answer
(A) In vertical,
initial vertical velocity, v0y = 25 sin34 = 13.98 m/s
ay = - g = - 9.8 m/s^2
at highest point, vertical velcoity will be zero.
Applying vf^2 - vi^2 = 2 a d
0^2 - 13.98^2 = 2 (-9.8) (Hmax)
Hmax = 9.97 m
(B) at highest point, vertical component will be zero so there will be only horizontal component.( that is constant throughout)
v = v0x = 25 cos34 = 20.725 m/s
(c) X = v0x t
t = 49.6 / (20.725) = 2.393 sec
y = v0y t + ay t^2 /2
H = (13.98 x 2.393) - (9.8 x 2.393^2 / 2)
H = 5.40 m
(D ) vx = 20.725 m/s
vy = 13.98 - (9.8 x 2.393) = -9.47 m/s
v = 20.72 i - 9.47 j
(e) speed = magnitude of v = sqrt(vx^2 + vy^2 ) = 22.8 m/s
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