Mechanical energy is equal to:
- A.Kinetic energy + Chemical energy
- B.Kinetic energy + Potential energy
- C.Kinetic energy + Heat energy
- D.Kinetic energy + Electrical energy
Correct answer
Explanation
The correct answer is B, Kinetic energy + Potential energy. The mechanical energy of a body is the sum of the energy of its motion and the energy of its position. Kinetic energy is half m v squared and gravitational potential energy is mgh, and their total stays the same as long as only gravity acts and friction is absent. That is the law of conservation of mechanical energy: a ball thrown upward loses kinetic energy and gains exactly as much potential energy, and a falling ball does the reverse, which is why a simple pendulum keeps swinging between the same two heights. When friction or air resistance acts, part of the mechanical energy turns into heat and sound, so it is no longer conserved, although the total energy of the system still is. Option A is wrong because chemical energy is stored in the bonds of fuels and food. Option C is wrong because heat is the energy of random molecular motion and is counted separately. Option D is wrong because electrical energy comes from moving charges. Exam tip: mechanical energy equals KE plus PE, and it stays constant only when no friction acts.
Practice Questions
View allThe fact that the planets move around the Sun, not in circles but in ellipses, was first demonstrated by
- A.Galileo
- B.Martin Luther
- C.Johannes Kepler
- D.Copernicus
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In 1609 Kepler showed that the planets move around the Sun in elliptical orbits, with the Sun at one focus of the ellipse.
Read the full explanation →Which one of the following statements is correct?
- A.Urea is produced in liver.
- B.Urea is produced in blood.
- C.Urea is produced from digestion of starch.
- D.Urea is produced in lung and kidney.
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Liver cells turn the toxic ammonia released from the breakdown of amino acids into urea through the ornithine cycle, also called the urea cycle.
Read the full explanation →Which one of the following is the correct sequence of passage of light in a compound microscope?
- A.Condenser-Objective lens-Eyepiece-Body tube
- B.Objective lens-Condenser-Body tube-Eyepiece
- C.Condenser-Objective lens-Body tube-Eyepiece
- D.Eyepiece-Objective lens-Body tube-Mirror
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Light passes through the condenser to the specimen, is picked up by the objective lens, travels up the body tube and reaches the eye through the eyepiece.
Read the full explanation →Which one of the following statements regarding haemoglobin is correct?
- A.Haemoglobin present in RBC can carry only oxygen but not carbon dioxide.
- B.Haemoglobin of RBC can carry both oxygen and carbon dioxide.
- C.Haemoglobin of RBC can carry only carbon dioxide.
- D.Haemoglobin is only used for blood clotting and not for carrying gases.
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It binds oxygen at its iron-containing haem groups and carries some carbon dioxide on its protein chains. Each haemoglobin molecule has four polypeptide chains and four haem groups, and each haem iron can hold one oxygen molecule, forming oxyhaemoglobin in the lungs.
Read the full explanation →Which one of the following statements regarding histone proteins is correct?
- A.Histones are proteins that are present in mitochondrial membrane.
- B.Histones are proteins that are present in nucleus in association with DNA.
- C.Histones are proteins associated with lipids in the cytosol.
- D.Histones are proteins associated with carbohydrates in the cytosol.
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They are the proteins around which DNA winds to form chromatin in the nucleus of eukaryotic cells. Histones are small basic proteins, rich in the positively charged amino acids lysine and arginine, which attract the negatively charged phosphate groups of DNA.
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