Work done concepts

Q: A man has less total energy after he performed work on another object.
False. Metabolism and respiration would replensih the energy used by the man.

Q: When some amount of fuel is used, the universe has less energy
False. This is only a transformation of energy. By the Law of Conservation of Energy, energy can neither be created nor destroyed.

Q: The KE of an object must be changed if its momentum is changed
False. KE is a scalar quantity, whereas momentum is a vector quantity. There may happen in a change in direction of a moving object, but with the speed be kept constant. This results in a change in momentum, but not a change in kinetic energy.

Q: A car must develop a larger power to move up an inclined road
True. It is because there is an increase in potential energy of the car.

Q: There is a larger work done against friction when moving up an inclined road
False. The friction is reduced because of a decrease in normal reaction on an inclined road.
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Q: When the truck leaves the spring, the momentum of the truck has changed while the KE of the truck remains unchange.
Yes. KE is a scalar quantity, whereas momentum is a vector quantity. The direction of the truck has changed, but the speed remains unchanged. This results in a change in momentum, but not a change in kinetic energy.