A cannon ball is shot horizontally off a 37.0 m cliff and lands a distance of 18.5 m
from the base of the cliff. Whall was the initial horizontal velocity of the cannon ball?

Respuesta :

Answer:

vₓ = 6.73 m/s

Explanation:

  • Assuming no other external influences than gravity, in the horizontal direction (which we make to coincide with the x- axis) , speed is constant, so, applying the definition of average velocity, we can write the following equation:

       [tex]v_{x} = \frac{\Delta x}{\Delta t} (1)[/tex]

  • Now, in the vertical direction (coincident with the y- axis) , as both movements are independent each other, initial velocity is zero, so we can write the following equation for the vertical displacement:

       [tex]\Delta h = \frac{1}{2} * g * t^{2} (2)[/tex]

  • where Δh = -37.0 m , g = -9.8 m/s2
  • Solving (2) for t, we get:

       [tex]t = \sqrt{\frac{2*\Delta h}{g} } =\sqrt{\frac{2*37.0m}{9.8m/s2}} = 2.75 s (3)[/tex]    

  • Taking t₀ = 0, ⇒ Δt = t
  • Replacing (3) in (1), we get:

       [tex]v_{x} = \frac{\Delta x}{\Delta t} = \frac{x}{t} = \frac{18.5m}{2.75s} = 6.73 m/s[/tex]

  • As the horizontal velocity is constant, the initial horizontal velocity is just the average one, i.e., 6.73 m/s.
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