The correct sequence of energy transfer that occurs when an apple falls to the ground is
- A.Gravitational potential energy → heat energy to air → kinetic energy → heat energy to ground and apple → sound energy
- B.Gravitational potential energy → sound energy → kinetic energy → heat energy to air → heat energy to ground and apple
- C.Gravitational potential energy → kinetic energy → heat energy to air → heat energy to ground and apple → sound energy
- D.Gravitational potential energy → kinetic energy → sound energy → heat energy to air → heat energy to ground and apple
Correct answer
Explanation
The correct answer is C. The apple's gravitational potential energy first becomes kinetic energy as it falls, some is lost as heat to the air on the way, and at impact the rest goes into heating the ground and apple and into sound.
An apple hanging on a tree stores potential energy equal to mgh. As it falls, its height drops and its speed rises, so potential energy turns into kinetic energy. Air resistance acts throughout the fall and turns a small part of this energy into heat in the air. When the apple strikes the ground, its kinetic energy is suddenly removed: most of it warms the apple and the ground slightly, and a little leaves as the sound of the thud. The total energy stays the same throughout, as the law of conservation of energy requires.
A is wrong: heating of the air cannot come before the apple starts moving.
B is wrong: sound is produced only at impact, not before the apple gains speed.
D is wrong: heat to the air is produced during the fall, before the sound at impact.
Exam tip: falling body: PE → KE, air friction → heat, impact → heat and sound.
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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