Estimate the force a person must exert on a string attached to a 0.145 kg ball to make the ball revolve in a horizontal circle. The ball makes 2.20 revolutions per second (T = 0.455 s ). Don't ignore the weight of the ball which revolves on a string 0.500 m long.

An electron is trapped at a defect in a crystal. the defect may be modeled as a one-dimensional, rigid-walled box of width 1.00 nm. (a) sketch the wavefunctions and probability densities for the n 1 and n 2 states. (b) for the n 1 state, nd the probability of nding the electron between x1 0.15 nm and x2 0.35 nm, where x 0 is the left side of the box. (c) repeat (b) for the n 2 state. (d) calculate the energies in electron volts of the n 1 and n 2 states