Question

A 52 kg pole vaulter running at 11 m/s vaults over the bar. Her speed when she is above the bar is 1.2 m/s. The acceleration of gravity is 9.8 m/s 2 . Find her altitude as she crosses the bar. Neglect air resistance, as well as any energy absorbed by the pole. Answer in units of m.

Answer 1

Answer:

6.1 m

Explanation:

m = Mass of person = 52 kg

h = Altitude

v = Velocity

Kinetic energy of the person on the ground

$\dfrac{1}{2}mv^2=\dfrac{1}{2}52\times 11^2\\ =3146\ J$

Kinetic energy of the person at the top

$\dfrac{1}{2}52\times 1.2^2\\ =37.44\ J$

At the top the potential energy is given by

$mgh=52\times 9.8h$

Balancing the energy of the system

$3146=37.44+52\times 9.8h\\\Rightarrow h=\dfrac{3146-37.44}{52\times 9.8}\\\Rightarrow h=6.1\ m$

Her altitude is 6.1 m