# calculating the loss of energy

• Mar 22nd 2011, 01:22 PM
poirot
calculating the loss of energy
A tennis ball of mass 60g is launched from ground level vertically upwards with a
speed of 30 m/s and reaches a height of 15m. Compute the loss of energy due to air
resistance.

I believe the loss of energy is equal to the work done. So i'm looking for force x distance
but am unsure about the force. My answer would be 60 x 9.8 x 15 but then why give me the speed
• Mar 22nd 2011, 02:04 PM
skeeter
Quote:

Originally Posted by poirot
A tennis ball of mass 60g is launched from ground level vertically upwards with a
speed of 30 m/s and reaches a height of 15m. Compute the loss of energy due to air
resistance.

I believe the loss of energy is equal to the work done. So i'm looking for force x distance
but am unsure about the force. My answer would be 60 x 9.8 x 15 but then why give me the speed

the initial energy of the ball is all kinetic energy ...

\$\displaystyle E_0 = \dfrac{1}{2}mv^2\$

the final energy of the ball is all gravitational potential energy ...

\$\displaystyle E_f = mgh\$

energy "loss" ...

\$\displaystyle \Delta E = E_f - E_0\$
• Mar 22nd 2011, 02:16 PM
poirot
Quote:

Originally Posted by skeeter
the initial energy of the ball is all kinetic energy ...

\$\displaystyle E_0 = \dfrac{1}{2}mv^2\$

the final energy of the ball is all gravitational potential energy ...

\$\displaystyle E_f = mgh\$

energy "loss" ...

\$\displaystyle \Delta E = E_f - E_0\$

Thanks.