A batter hits a baseball m = 0.41 kg from rest with a force of F = 81

N, The ball is in contact with the bat for t = 0.22 s. It is observed that the ball leaves the bat

with an angle of 0 = 29 degrees with respect to the horizontal.

How long was the ball in the air if it was hit from the top of the cliff with a height of h=86m?

Respuesta :

Answer:

7.0s

Explanation:

Mass = 0.41kg

F= 81N

t = 0.22s

¤ = 29°

Lo = 86m

From impulse equation,

F*t = m* v

81 * 0.22 = 0.41 * v

Vo = 17.82 / 0.41

Vo = 43.46m/s

Vx= velocity across horizontal plane

Vy = velocity across vertical plane

Vx = Vo * cos ¤

Vy = Vo * sin ¤

Vx = 43.46 * cos 30° = 37.64 m/s

Vy = 43.46 sin 30° = 21.73 m/s

Distance travelled across the vertical plane,

L = Lo + Vy *t + ½gt²

0 = 86 + 21.73t - 4.9t²

4.9t² - 21.73t - 86 = 0

Solving for t in the quadratic equation,

t = 6.96 or -10.04

Using the positive root since time can't be negative, t = 6.96 approximately 7.0s

The time spent in the air by the ball during the motion is 6.9 s.

The given parameters;

  • mass of the baseball, m = 0.41 kg
  • force applied on the ball, F = 81 N
  • time of the force action, t = 0.22 s
  • height of the cliff, h = 86 m.

The velocity of the ball when hit by the bat is calculated as follows;

[tex]F = ma = \frac{mv}{t} \\\\mv = Ft\\\\v = \frac{Ft}{m} \\\\v = \frac{81 \times 0.22}{0.41} \\\\v = 43.46 \ m/s[/tex]

The time of motion of the ball is calculated as follows;

[tex]h = h_0 + v_y t - \frac{1}{2} gt^2\\\\0 = 86 + (vsin\theta)t - (0.5 \times 9.8 \times t^2)\\\\0 = 86 + (43.46\times sin(29))t \ - \ 4.9t^2\\\\0 = 86 + 21.1 \ t - 4.9 t^2\\\\4.9t^2 - 21.1 t - 86= 0\\\\solve\ the \ quadratic \ equation \ using \ formula \ method;\\\\a = 4.9, \ b = -21.1 , \ c = -86\\\\t = \frac{-b \ \ +/- \ \ \sqrt{b^2 - 4ac} }{2a} \\\\t = \frac{-(-21.1) \ \ +/- \ \ \sqrt{(21.1)^2 - 4(4.9\times -86)} }{2(4.9)}\\\\t = 6.9 \ s[/tex]

Thus, the time spent in the air by the ball is 6.9 s.

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