A boy is swinging a yo-yo with mass 0.5 kg in a circle with radius 0.7 m at a speed of 7 m/s. What is the tension in the string connecting the yo-yo to the
boy's finger, disregarding the effect of gravity?

A. 35 N

B. 20 N

C. 9 N

D. 12 N

The nuclear potential that binds protons and neutrons in the nucleus of an atom is often approximated by a square well. imagine a proton conned in an innite square well of length 105 nm, a typical nuclear diameter. calculate the wavelength and energy associated with the photon that is emitted when the proton undergoes a transition from the rst excited state (n 2) to the ground state (n 1). in what region of the electromagnetic spectrum does this wavelength belong?