I am only a HS Freshman so I might be wrong
Answer:
3. Its potential energy and the formula for PE = mgh so you would use the weight given (Weight = mg) and mg is in the (Potential Energy) forumula so we multiply 3 by 30 and get 90 Joules
4. We would do the same thing with this: PE = mgh; PE = 10*3 = 30 Joules
Once again I am only a Freshman and I have taken Private AP Physics classes so just maybe wait for someone who is more confident.
This is just what I would answer
btw, for problem 5, the fromula for kinetic energy is 1/2*m*v^2
