The Law of the Conservation of Energy is stating that the total mechanical energy is always conserved or in simpler terms, not used or saved.
Answer:
the application of scientific knowledge for practical purposes, especially in industry. Another answer:the sum of techniques,skills,methods and processes used in the production of goods or services or in the accomplishment of objectives, such as scientific investigation
Weight equals mass times gravitational acceleration=400N, so mass=400/9.8=41kg approx.
C. Lack of mates. If they cannot reproduce enough, their size will reduce.