Question

A child sleds down a frictionless hill with vertical drop h. At the bottom is a level stretch where the coefficient of friction is 0.27.If she slides 19 m across the level stretch, what's h? Express your answer with the appropriate units.

Answer 1

E = mgh

where m is the mass of the sled, g is the acceleration due to gravity, and h is the height of the hill.

At the bottom of the hill, all of the potential energy has been converted into kinetic energy, which is given by:

E = (1/2)mv^2

where v is the velocity of the sled at the bottom of the hill.

When the sled reaches the level stretch, the kinetic energy is converted into work done by the friction force, which is given by:

W = fd

where f is the friction force and d is the distance traveled across the level stretch.

Setting the potential energy at the top of the hill equal to the work done by the friction force on the level stretch, we have:

mgh = fd

Solving for h, we get:

h = (fd)/(mg)

Substituting the given values, we get:

h = (0.27)(m)(9.8 m/s^2)(19 m)/(m)(9.8 m/s^2)

Simplifying, we get:

h = 5.13 m

Therefore, the height of the hill is 5.13 meters.