Answer:
If the system consists of the block only, the work done by the gravity is negative.
If the system consists of the block and the earth the work done by the gravity is zero.
Explanation:
If the system consists of the block only, then the system experiences two external forces: one exerted by the hand that lifts the block vertically upward and other exerted by the earth (gravity), which is opposed to the movement of the system, so the work done by gravity is negative.
On the other hand, if the system consists of the block and the earth, then only exists a external force which is the exerted by the hand. So, the force exerted by gravity is zero.
The answer is evolution. When a specifies evolves over time they change and adapt to their environment.
A water wave is an example of a mechanical wave. A wave that can travel only through matter is called a mechanical wave.
It's true charged particles are always acted on by an electric field.when the velocity of the electron is parallel to the magnetic field, the magnetic force vanishes.
