8) A soccer goal is 2.44 m high. A player kicks the ball at a distance 10.0 m from the goal at an angle of 25.0°. The ball hits the crossbar at the top of the goal. What is the initial speed of the soccer ball?

Respuesta :

Answer:

The initial speed of the soccer ball is 16.38 m/s

Explanation:

given;

vertical distance y = 2.44 m

horizontal distance x = 10.0 m

angle of projection θ = 25.0°

Initial velocity has two components, Vₓ and V[tex]_y[/tex]

Vₓ  = V[tex]_i[/tex] cosθ

V[tex]_y[/tex] = V[tex]_i[/tex] sinθ

The horizontal distance = x = Vₓt + ¹/₂ ˣ g ˣ t², but g =0

x = Vₓt =  V[tex]_i[/tex] cosθ *t

10 = V[tex]_i[/tex] cos25 *t

10 = 0.906V[tex]_i[/tex]*t

V[tex]_i[/tex]*t = 10/0.906 = 11.038 m

The vertical distance (g = - g, because it upward motion against gravity)

y = V[tex]_y[/tex]*t -¹/₂ ˣ g ˣ t²

2.44 = (V[tex]_i[/tex] sinθ)t - ¹/₂ ˣ 9.8 ˣ t²

2.44 = (V[tex]_i[/tex]*t)sinθ - ¹/₂ ˣ 9.8 ˣ t²

2.44 = (11.038)sin25° - 4.9t²

2.44 = (11.038)*0.4226 - 4.9t²

2.44 = 4.6647 - 4.9t²

4.9t² = 4.6647 - 2.44 = 2.2247

t² = 2.2247/4.9

t² = 0.454

t = √0.454

t = 0.674 s

Recall that V[tex]_i[/tex]*t = 11.038 m

V[tex]_i[/tex]*0.674 = 11.038 m, solve for V[tex]_i[/tex]

V[tex]_i[/tex] = 11.038/0.674

V[tex]_i[/tex] = 16.38 m/s

Therefore, the initial speed of the soccer ball is 16.38 m/s

The initial speed of the soccer ball is 16.38 m/s

given information:

vertical distance y = 2.44 m

horizontal distance x = 10.0 m

angle of projection θ = 25.0°

horizontal equation of motion:

The horizontal distance is given by:

since there is no force in the horizontal direction.

[tex]x = V_xt = Vcos\theta \times t\\\\10 = Vcos25 \times t\\\\10 = 0.906Vt\\\\Vt = 11.038 m\\\\[/tex]

vertical equation of motion:

The vertical distance is given by:

[tex]y = V_yt -\frac{1}{2} gt^2\\\\2.44 = (Vsin\theta)t - 0.5\times9.8t^2\\\\2.44 = (11.038)sin25 - 4.9t^2\\\\2.44 = (11.038)\times0.4226 - 4.9t^2\\\\2.44 = 4.6647 - 4.9t^2\\\\4.9t^2 = 4.6647 - 2.44\\\\t^2 = 2.2247/4.9\\\\t^2 = 0.454\\\\t = 0.674 s\\\\[/tex]

Now,

[tex]Vt = 11.038\\\\V\times0.674 = 11.038\\\\V = 11.038/0.674\\\\V = 16.38 m/s[/tex]is the initial speed of the soccer ball.

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