Which of the following is a true statement? a. electromagnetic waves are longitudinal waves. b. electromagnetic waves do not always need a medium to travel. c. electromagnetic waves consist of only changing electric fields. d. electromagnetic waves can vary in speed, wavelength and frequency.

With i really need the correct answer!

A30 kg weight lies on top of a massless piston of area a = 0.01 m2 the exterior air is at a (constant) p =1 atm and t = 27 c. the interior gas is 0.4 moles of (ideal) n2 and it has initial temperature 27.00 degrees c. 1. what is the initial pressure in the interior? a. 29.4 kpa b. 130.7 kpa c. 101.3 kpa the next three questions concern what happens when an amount of heat q is slowly added to the interior, raising the piston by 1 mm and raising the interior temperature to 27.40 c

Which articulations allow for greatest range of motion?