two coins lie 1.5 meters apart on a table. they carry identical electric charges. approximately how large is the charge on each coin if each coin experiences a force of 2.0 N

The energy equivalent of the rest mass of an electron is

Estimate the kinetic energy of mars with respect to the sun as the sum of two terms, that due to its daily rotation about its axis, and that due to its yearly revolution about the sun. (assume mars is a uniform sphere with mass = 6.4×10 to the power of 23 kg, radius = 3.4×10 to the power of 6 m, rotation period = 24.7 hours, orbital period = 686 days and is 2.3×10 to the power of 8 km from the sun.)

If frequency goes down, what happens to wavelength? does it get shorter or longer?