A skier starts from rest at the top of a ski slope and skis downhill. Find the skier's speed after her elevation decreases by 10m, assuming no work is done by friction or air resistance.

Explanation

Change in PE of the skier when her elevation decreases by `10 m, i.e., E_p = mgh` Since no work is done against friction or air resistance, `E_p` is converted into the kinetic energy
`((1)/(2)mupsilon^2)` of the skier, i.e., `E_p = (1)/(2) m upsilon^2 or mgh = (1)/(2)m upsilon^2`
or `upsilon = sqrt(2gh) = sqrt (2(9.8)(10)) = 14m//s` (as h = 10m)