If a roller coaster has a gravitational potential energy of 15J and kinetic energy of 5J, what is the mechanical energy?

Why should the wavelength scale of spectroscope be calibrated

An electron moving at 5.06 103 m/s in a 1.23 t magnetic field experiences a magnetic force of 1.40 10-16 n. what angle does the velocity of the electron make with the magnetic field? there are two answers between 0° and 180°. (enter your answers from smallest to largest.)

5400 j of energy are given off when a 50 g of aluminum pan changes temperature. does the temperature of the pan increase or decrease and by how much?