8.5. Energy Problem Solving http://www.ck12.org
- An elevator in an old apartment building in Switzerland has four huge springs at the bottom of the shaft to
cushion its fall in case the cable breaks. The springs have an uncompressed height of about 1 meter. Estimate
the spring constant necessary to stop this elevator, following these steps:
a. First, guesstimate the mass of the elevator with a few passengers inside.
b. Now, estimate the height of a five-story building.
c. Lastly, use conservation of energy to estimate the spring constant. - You are skiing down a hill. You start at rest at a height 120 m above the bottom. The slope has a 10. 0 ◦grade.
Assume the total mass of skier and equipment is 75.0 kg.
a. Ignore all energy losses due to friction. What is your speed at the bottom?
b. If, however, you just make it to the bottom with zero speed what would be the average force of friction,
including air resistance?- Two horrific contraptions on frictionless wheels are compressing a spring(k=400 N/m)by 0.5 m compared
to its uncompressed (equilibrium) length. Each of the 500 kg vehicles is stationary and they are connected by
a string. The string is cut! Find the speeds of the vehicles once they lose contact with the spring. - A roller coaster begins at rest 120 m above the ground, as shown. Assume no friction from the wheels and air,
and that no energy is lost to heat, sound, and so on. The radius of the loop is 40 m.
a. If the height at point G is 76 m, then how fast is the coaster going at point G?
b. Does the coaster actually make it through the loop without falling? (Hint: You might review the material
from centripetal motion lessons to answer this part.)