Atrain travels 77 kilometers in 4 hours, and then 76 kilometers in 2 hours. what is its average speed?

How does the amount of energy required to hold each proton and neutron in the nucleus compare to the energy released when they are removed?

The boy of mass 30 kg is at r1= 2 meters from the fulcrum. of the girl is 45 kg, at what r2 must she sit so that they are balanced ?

Africtionless piston-cylinder contains 50 l of saturated liquid r-134a. the piston has a mass and an area resulting in an applied pressure of 500 kpa on the refrigerant. the refrigerant is now heated until its temperature rises to 70∘c. calculate the work (in kj) done during this process.