What is the gravitational potential energy of a book with a mass of 0.30 kg on a 1.0 m high desk?

An automobile of mass 2000 kg moving at 30 m/s is braked suddenly with a constant braking force of 10000 n. how far does the car travel before stopping?

If a spring has a k value of 100 newtons per meter and it is stretched 0.50 meters, what is the restoring force of the spring?

Which is the correct symbol for an isotope of iodine with 53 protons and 78 neutrons?