Speed of light and sound

During a thunderstorm, we first see the lightning and then hear the thunder. Assume that clouds and storm occur in the lower reaches of the earth's atmosphere, which is approximately 5km above the earth's surface. How long after you see the lightning do you hear the thunder?

Frequency and wavelength

The speed of electromagnetic waves through vacuum or air is 3X10^8m/sec. Find the frequency of the green light with a wavelength of 5.4X10^-7m and the wavelength of radio waves broadcast at 900kilohertz.

Magnitude and KE

A 1000-kg Volkswagen with speed 30m/sec collides head-on with a large truck of mass 10,000kg and speed 25m/sec. As a result of the collision, the two vehicles lock together. a. Find the magnitude and the direction of the velocity of the vehicles right after the collision. b. Compute the total Kinetic energies before and after the collision. c. Is the collision elastic or inelastic?

Electrostatic force

If the electrostatic force between to protons is equal to 1X10^-7 Newtons, what is the distance between them?

Magnitude

A positive charge of 2X10-12 Coulombs placed 10cm from another charge experiences a repulsive force of 9X10-9 Newtons. What is the sign and magnitude of the other charge?