A projectile is fired with an initial muzzle speed 570 m/s at an angle 40∘ from a position 6 meters above the ground level. Find the horizontal displacement from the firing position to the point of impact. At what speed does the projectile hit the ground?

Respuesta :

Answer:

x  =  32356.44 m

|V |  = 567,02 m/s

θ = 42  ( second quadrant )

Step-by-step explanation:

With V₀ = 570 m/s       and      θ = 40°   ( angle above horizontal)

we get

Vox   =  Vo* cos θ      Vox   = 570 * 0,7660         Vox = 432.62 m/s

Voy   =  Vo* sin θ       Voy   = 570 * 0.6428         Voy = 366,40 m/s

Just at the moment of ground impact  y  =  0

y  =  y₀ + Voy * t  - 1/2 g*t²

By subtitution

0  =  6  + 366,40*t  -  4.9*t²

In this second degree equation we solve for x

4.9*t²  - 366.40*t  - 6  = 0

t₁,₂  = [ 366.40 ± √ (366.40)² + 117.6] / 9.8

t₁  =  -0.16/9.8    we dismiss this negative root

t₂ = 74.79 s       which is the total time of the movement

Then x the horizontal displacement is:

x  =  Vox * t        x  = 432.62 * 74.79        x  =  32356.44 m

To find the speed of the projectile hitting the ground

Vy  = Voy - g*t            Vy  = 366.40 - 9.8 * 74.79        Vy = 366,54  m/s

Then V = √ (Vx)² + (Vy)²       V = √ (432.62)² + (366.54)²

|V |  = 567,02 m/s

and the angle is  

θ = arctan ( Vy/Vx)       θ = arctan - 366.54/432,62     θ = arctan -0.85

θ = 42 ( angle between the projectile and the horizontal axis (second quadrant)