Question

In the javelin throw at a track-and-field event, the javelin is launched at a speed of 29 m/s at an angle of 36???? above the horizontal. As the javelin travels upward, its velocity points above the horizontal at an angle that decreases as time passes. How much time is required for the angle to be reduced from 36???? at launch to 18?????

Answer 1

Answer:

t = 0.96 s  is the time it takes for the angle to reduce

Explanation:

In the launch of projectiles, the velocity is broken down into its x and y components, the velocity in the x-axis is constant, as there is no acceleration, instead the velocity in the axis and is reduced by the effect of the acceleration of gravity.

We can find Vox for the initial conditions

  Voy  = Vo sin θ

  Voy = 29 sin 36

  VoY = 17 m/s

  Vox = Vo cos θ

  Vox = 29 cos 36

  Vox= 23.5 m/s

  Vx = Vox  

The velocity on the x axis is constant

By trigonometry, we find the firing angle

 

  tan θ = Voy/ Vx

  Vy = Vx tan θ

  Vy = 23.5 tan 18

  Vy = 7.64 m/s

Now that we have the vertical speed we can find the time

   Vy = I'm going - g t

   t = (Vy -Voy) / g

   t = (17 - 7.64) /9.8

   t = 0.96 s

Be the time it takes for the angle to reduce