Tag: science & technology

When a body rests on a horizontal surface without external forces, two forces act on it: its weight (downward) and the normal reaction force (upward) from the surface. Since the question specifically asks about forces from the ground/surface, 'normal reaction' (B) is the correct answer. Friction only acts when there's motion or tendency to move.

William Harvey discovered the mechanism of blood circulation in 1628 and published his findings in 'De Motu Cordis' (On the Motion of the Heart), proving that the heart acts as a pump circulating blood throughout the body in a continuous loop. Gregor Mendel is associated with genetics, Kepler with astronomy, and Faraday with electromagnetism.

Henry Cavendish discovered hydrogen in 1766 and termed it 'inflammable air,' recognizing it as a distinct substance with unique properties. He identified hydrogen gas by observing that it was produced when acids reacted with metals.

Michael Faraday formulated the quantitative laws of electrolysis in 1833, describing the relationship between the amount of substance deposited at electrodes and the electric charge passed through the solution. Humphry Davy discovered several elements using electrolysis but did not establish the mathematical laws.

Isaac Newton formulated the Law of Universal Gravitation in 1687, published in his Principia Mathematica. J.J. Thompson discovered the electron, Christian Barnard was a heart surgeon, and Michael Faraday worked on electromagnetism.

Gregor Mendel discovered the fundamental laws of heredity through his pea plant experiments (1856-1863), establishing the principles of segregation and independent assortment. Davy worked in chemistry, Hans Christian Oersted in electromagnetism, and Newton in physics.

Ernest Rutherford supervised the famous gold foil experiment in 1909, which was actually conducted by Hans Geiger and Ernest Marsden under his guidance. The experiment led to the discovery of the atomic nucleus. J.J. Thomson discovered the electron, James Chadwick discovered the neutron, and Lew Kowarski was a nuclear physicist not associated with this experiment.

The gold foil experiment's main outcome was discovering that atoms have a small, dense, positively charged nucleus at their center, with most of the atom being empty space. This revolutionized atomic theory. Neutrons, protons, and electrons were either discovered later or through different experiments - the nucleus itself was the key discovery here.

Chemical properties of elements are primarily determined by valence electrons - the electrons in the outermost shell. These electrons participate in bonding and chemical reactions. Inner electrons and the nucleus don't directly participate in chemical bonding. Protons determine nuclear charge and atomic number, not chemical behavior.

James Chadwick discovered the neutron in 1932, confirming its existence as a neutral particle in the nucleus. Rutherford had predicted the neutron's existence earlier but didn't discover it. Niels Bohr developed the Bohr model of the atom, and J.J. Thomson discovered the electron, not the neutron.