Answer:
80%
Explanation:
Efficiency of machine = work output/work input ×100 %
From question, work output = 20J
Work input = 25J.
Therefore efficiency = 20/25 × 100 %
Efficiency = 20×4 %
Efficiency = 80%
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Answer:
Elements in a period have wide range of chemical properties.
Explanation:
- Period is the row of chemical elements's arrangement in the periodic table. It is numbered from 1 to 7.
- In period as we move towards right the atomic number of element constantly increases along with the change in chemical properties.
- As we move from left towards right in period, the valence electron number regularly increases in every element.
- This valence electron differs the reactivity of the elements.
Answer:
Correct sentence: gravitational potential energy of the mass on the hook.
Explanation:
The mechanical energy of a body or a physical system is the sum of its kinetic energy and potential energy. It is a scalar magnitude related to the movement of bodies and to forces of mechanical origin, such as gravitational force and elastic force, whose main exponent is Hooke's Law. Both are conservative forces. The mechanical energy associated with the movement of a body is kinetic energy, which depends on its mass and speed. On the other hand, the mechanical energy of potential origin or potential energy, has its origin in the conservative forces, comes from the work done by them and depends on their mass and position. The principle of conservation of energy relates both energies and expresses that the sum of both energies, the potential energy and the kinetic energy of a body or a physical system, remains constant. This sum is known as the mechanical energy of the body or physical system.
Therefore, the kinetic energy of the block comes from the transformation in this of the gravitational potential energy of the suspended mass as it loses height with respect to the earth, keeping the mechanical energy of the system constant.
A cloud in space that is composed of dust and gas is call a nebula. The word "nebula" is derived from the Latin word for "cloud," and nebulae in space are indeed large interstellar clouds made up of dust, hydrogen, helium and plasma.
