I think the correct answer from the choices listed above is option D. The difference between a chemical change and a physical change is lies in the fact that a physical change does not break any bonds while a chemical change does form new substances. Hope this answers the question.
Answer: gravitational force between them will be reduced by one - fourth ( 1/4) of its initial value.
Explanation: Gravitational force between two bodies obeys inverse square law. That is, gravitational force between two bodies is inversely proportional to the square of the distance between the two bodies.
When the mammoth is at a distance that is twice the original distance, the gravitational force between them will be reduced by one - fourth ( 1/4 ) of its initial value.
Explanation:
The total energy of the system remains conserved. It just converts from one form of energy to another.
The battery of the cell phone contains chemicals. As the electricity is passed through the cell phone, the electrical energy is converted to chemical energy. As she notices that the phone is warm and after the battery has been fully charged and the student unplugs her cell phone, the phone vibrates when a message arrives, this shows the conversion of chemical energy to mechanical energy, thermal energy etc.
Hence, we can say that the correct option is (b).
Answer:

Explanation:
To solve this problem we use the formula for accelerated motion:

We will take the initial position as our reference (
) and the downward direction as positive. Since the rock departs from rest we have:

Which means our acceleration would be:

Using our values:
