A 52-kg pole vaulter running at 10 m/s vaults over the bar. Her speed when she is above the bar is 1.2 m/s. Neglect air resistance, as well as any energy absorbed by the pole, and determine her altitude as she crosses the bar.

Respuesta :

Answer:

The altitude is 5.03 m

Explanation:

Given:

Mass of pole [tex]m = 52[/tex] kg

Speed of vaulter [tex]v_{i} = 10\frac{m}{s}[/tex]

Speed of vaulter when she is above the bar [tex]v_{f} = 1.2 \frac{m}{s}[/tex]

For finding altitude we use conservation of energy,

          [tex]\Delta E _{i} = \Delta E _{f}[/tex]

  [tex]\frac{1}{2} m v_{f} ^{2} + mgh= \frac{1}{2} m v _{i} ^{2} +0[/tex]         ( ∵ initial height is zero )

    [tex]v_{i} ^{2} - v_{f} ^{2} = 2g h[/tex]

   [tex]h = \frac{v_{i} ^{2} - v_{f} ^{2}}{2g}[/tex]

   [tex]h = \frac{100-1.44}{2 \times 9.8}[/tex]                           ( ∵ [tex]g = 9.8 \frac{m}{s^{2} }[/tex] )

   [tex]h = 5.03[/tex] m

Therefore, the altitude is 5.03 m