Question

A 8 kg ball is dropped off the top of a 30m building. Show that the speed of the ball just before it strikes the ground is 24.2 m/s using:

a. The equation of kinematics for 1-dimensional motion. Use: Vfy^2 - Viy^2 = -2y(yf - yi)

b. The conservation of Mechanical energy.Use: KEi + PEi = KEf + PEf

c. Suppose we did not know the spring constant for the spring in problem 1. If given unlimited resources, describe how you could determine the spring constant experimentally.

Answer 1

c) to find spring constant experimentally hang the mass in spring and allow to oscillate (fix other end in a rigid support). note mean position and maximum stretched distance of spring. take the difference of positions,

now you can equate stored spring energy and potential energy dissipated. sping energy = 05*k*x²

and potential energy = mgx . b equating two you get k=2mg/x