6. A boy falls and hits his head with an impulse of 30.N. s. On the sand, the boy would hit for .60s. What force did the sand exert on the boy?

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.