In a 15-volt potential, a particle has a potential energy of -0.45 J. What is the particle's charge?

Need only answer if you think you know it

Mechanical energy is when the amount of kinetic and potential energies added together remains the same. conserved created lost

An astronaut in space cannot use a scale or balance to weigh objects because there is no gravity. but she does have devices to measure distance and time accurately. she knows her own mass is 77.4 kg , but she is unsure of the mass of a large gas canister in the airless rocket. when this canister is approaching her at 3.50 m/s , she pushes against it, which slows it down to 1.30 m/s (but does not reverse it) and gives her a speed of 2.60 m/s . what is the mass of the canister?