A moderate wind accelerates a pebble over a horizontal xy plane with a constant acceleration = (4.80 m/s2)î + (7.00 m/s2)ĵ. at time t = 0, the velocity is (4.4 m/s)î. what are magnitude and angle of its velocity when it has been displaced by 12.4 m parallel to the x axis?

Respuesta :

Acceleration, a = ( 4.80 i+7.00 j )[tex]m/s^2[/tex]

We have acceleration a = Horizontal component i + Vertical component j

                               So  Horizontal component =4.80 [tex]m/s^2[/tex]

                                      Vertical component =7.00 [tex]m/s^2[/tex]

We have horizontal displacement , [tex]s = ut+\frac{1}{2} at^2[/tex]

Here s = 12.4 m, u = 4.4 m/s and a = 4.80 [tex]m/s^2[/tex]

Substituting

              [tex]12.4 = 4.4*t+\frac{1}{2} *4.80*t^2\\ \\ t^2+1.83*t-5.167=0\\ \\ (t-1.53)(t+3.36)=0\\ \\ time = 1.53 seconds[/tex]

             Negative time is not possible.

Now we need to find velocity after 1.53 seconds

We have v = u+at

Horizontal case

        v = 4.4 + 4.80 * 1.53 = 11.744 i

Vertical case

        v = 0 + 7.00 * 1.53 = 10.71 j

So Velocity when it has been displaced by 12.4 m parallel to the x axis = (11.744 i+10.71 j) m/s

Magnitude = [tex]\sqrt{11.744^2+10.71^2} =15.89 m/s[/tex]

Angle , tan θ = [tex]\frac{10.71}{11.744}[/tex]

   θ = 42.36⁰