Why is it difficult to breathe at higher altitudes -

ssc Online Exam general science mcq questions and answers for competitive exams :: :: Home general science mcq questions and answers for competitive exams / Questions and Answers 4111. The hair of shaving brush clings together when removed from waterdue to A Elasticity B Friction C Viscosity D Surface tension View Answer Discuss in Forum Answer & Explanation Answer : Option D Explanation : Surface tension.Surface tension is a contractive tendency of the surface of a liquid that allows it to resist an external force.g. It is revealed, for example, in the floating of some objects on the surface of water, even though they are denser than water, & in the ability of some insects (e. water striders) to run on the water surface. This property is caused by cohesion of similar molecules, & is responsible for many of the behaviors of liquids. In the present case, as the forces inside the molecules of water also pulls in the hair on the shaving brush as they have less mass, due to this tension in the surface of the water the hair sticks together. 4112. Magnetism at the centre of a bar magnet is A Zero B Minimum C Maximum D Minimum or maximum View Answer Discuss in Forum 4113. Muscle fatigue is caused by the accumulation of: A Lactic acid B Oxalacetic acid C Uric acid D Pyruvic acid View Answer Discuss in Forum Answer & Explanation Answer : Option A Explanation : Lactic acid.It was once believed that lactic acid build-up was the cause of muscle fatigue. Produced as a by-product of fermentation, lactic acid can rise intracellular acidity of muscles. The assumption was lactic acid had a picklingeffect on muscles 4114. Which among the given gases will effuse out of football bladder most quickly - A N2 B O2 C H2 D He View Answer Discuss in Forum Answer & Explanation Answer : Option C Explanation : H2.Hydrogen is a chemical element with symbol H & atomic number 1.00794 u (1. With an average atomic weight of 1.007825 u for hydrogen-1), hydrogen is the lightest element & its monatomic form (H1) is the most abundant chemical substance, constituting roughly 75% of the Universes baryonic mass. Naturally occurring atomic hydrogen is rare on Earth as hydrogen readily forms covalent compounds with most elements & is present in the water molecule & in most organic compounds. 4115. The material used in the manufacture of lead pencil is A Graphite B Mica C Carbon D Lead View Answer Discuss in Forum Answer & Explanation Answer : Option A Explanation : Graphite.Pencils create marks via physical abrasion, leaving behind a trail of solid core material that adheres to a sheet of paper or other surface. Most pencil cores are made of graphite mixed with a clay binder, leaving grey or black marks that can be easily erased. They are noticeably distinct from pens, which dispense liquid or gel ink that stain the light colour of the paper. Graphite pencils are used for both writing & drawing, & the result is durable: although writing can usually be removed with an eraser, it is resistant to moisture, most chemicals, ultraviolet radiation & natural aging. Other types and categories of pencil core are less widely used. Charcoal pencils are mainly used by 4116. These waves cannot be transmitted through vacuum A Heat B Sound C Light D Electromagnetic View Answer Discuss in Forum Answer & Explanation Answer : Option B Explanation : Sound.Sound is a mechanical wave that is created by vibrating objects & propagated through a medium from one location to another. That is, mechanical waves cannot travel through a vacuum. As mechanical waves rely on particle interaction in order to transport their energy, they cannot travel through regions of space that are void of particles. 4117. Dry ice is the solid form of: A Water B Carbon diâ€oxide C Nitrogen D Air View Answer Discuss in Forum Answer & Explanation Answer : Option B Explanation : Carbon diâ€oxide.Dry ice, sometimes referred to as cardice, is the solid form of carbon dioxide. Its advantages include lower temperature than that of water ice & not leaving any residue. It is used primarily as a cooling agent. It is useful for preserving frozen foods, ice cream, etc., where mechanical cooling is unavailable. 4118. Which among the given colour of light deviates least through the prism - A red B violet C green D yellow View Answer Discuss in Forum Answer & Explanation Answer : Option A Explanation : In refracting media like glass prism, water, etc., lights of different colors travel with different speeds. The speed of violet colour is the least, while the speed of red colour is the largest in prism. As a result, the refractive index of glass is largest for violet colour & least for red colour. So the violet colour is deviated the most, while red colour is deviated least on passingthrough the prism. 4119. Rock salt is a mineral containing A iron B magnesium C sodium D potassium View Answer Discuss in Forum Answer & Explanation Answer : Option C Explanation : sodium.Halite, commonly known as rock salt, is the mineral form of sodium chloride (NaCl). It commonly occurs with other evaporite deposit minerals such as several of the sulfates, halides, & borates. Halite forms isometric crystals. 4120. pH value between 6.5-7.5 makes the soil A None of these B Basic C Neutral D Acidic View Answer Discuss in Forum Answer & Explanation Answer : Option A Explanation : In chemistry, pH is a measure of the activity of the (solvated) hydrogen ion. P [H], which measures the hydrogen ion concentration is closely associated to, & is often written as, pH. Pure water has a pH veryclose to 7 at 25°C. Solutions with a pH less than 7 are said to be acidic & solutions with a pH greater than 7 are basic or alkaline. A pH of 7 is treated as neutral. 4121. In radio-communication, the signals emitted by transmitting antenna are reflected on A troposphere B stratosphere C ionosphere D ozonosphere View Answer Discuss in Forum Answer & Explanation Answer : Option C Explanation : ionosphere.The lower atmosphere is more or less transparent to radiowaves. Thus, a signal emitted by an antenna from a certain place can be received at another place on the surface of Earth in the following two ways: ground wave propagation & sky wave propagation. However, the ionosphere reflects back the radio waves. 4122. When a semiconductor is heated, its resistance A Decreases B Trebles for every 10° C rise in temperature C Doubles for every 10° C rise in temperature D Does not change View Answer Discuss in Forum Answer & Explanation Answer : Option A Explanation : 4123. The quality of petrol is expressed in terms of A Gold number B Cetane number C Octane number D Added unlead compounds View Answer Discuss in Forum 4124. Which among the given statements is right? I. German silver is an alloy of silver, copper and zinc II. There is no zinc in brass III. Bronze is an alloy of copper and tin A I and II THE ATOM B Only III C I, II, and III D I and III View Answer Discuss in Forum Answer & Explanation Answer : Option B Explanation : 4125. Why is it difficult to breathe at higher altitudes - A Due to low temperature B Due to ozone C Due to high humidity D Due to low air pressure View Answer Discuss in Forum Answer & Explanation Answer : Option D Explanation : Due to low air pressure.Low air pressure is usually the most significant limiting factor in high mountain regions.2 km is essentially the same as at sea level (21%). The percentage of oxygen in the air at 3. However, the air pressure is 30% lower at the higher altitude due to the fact that the atmosphere is less dense-that is, the air molecules are farther apart. At high altitudes, the lower air pressure makes it more difficult for oxygen to enter our vascular systems. The result is hypoxia, or oxygen deprivation. In serious cases, pneumonia-like symptoms (pulmonary edema) due to hemorrhaging in the lungs & an abnormal accumulation of fluid around the brain (cerebral edema) develop. Pulmonary & cerebral edema usually results in death within a few days if there is not a return to normal air pressure levels. There is also an increased risk of heart failure due to the added stressplaced on the lungs, heart, & arteries at high altitudes.