Has there been signs that time travel exist

When electrons in an atom in an excited state fall to lower energy levels, energy is?

A wave has a frequency of 440 hz and a wavelength of 0.77m. What is the velocity of the wave

An ultrasound machine can measure blood flow speeds. Assume the machine emits acoustic energy at a frequency of 2.10 MHz, and the speed of the wave in human tissue is taken to be 1510.0 m/s.

When light is reflected, how are the angle of incidence and angle of reflection related

Which of the following are major problems with fission reactors? 1. Maintaining high temperatures 2. Disposal of hot water 3. Disposing of radioactive waste 4. Obtaining fuel

Why does ice generally have very little friction when it is in contact with other materials?

A stationary speed gun emits a microwave beam at 2.10*10^10Hz. It reflects off a car and returns 1030 Hz higher. What is the speed of the car?

Discuss the changes in potential energy and kinetic energy and total energy for skateboarder going up and down on a half pipe ramp

The diagram below shows rock is affected when water enters cracks in rock, freezes and becomes ice

A vertical piston-cylinder device contains a gas at a pressure of 100 kPa. The piston has a mass of 5 kg and a diameter of 12 cm. Pressure of the gas is to be increased by placing some weights on the piston.