An object with a mass of 22 kg moving with a velocity of 5 m/s possesses kinetic energy of:
- A.275 J
- B.110 J
- C.1100 J
- D.2750 J
Correct answer
Explanation
The correct answer is A, 275 J. Kinetic energy is half m v squared, so half of 22 multiplied by 5 multiplied by 5 gives 275 joules. Kinetic energy is the energy a body has because of its motion. It rises in direct proportion to the mass but with the square of the speed, so doubling the speed makes the energy four times larger, which is why a fast vehicle needs a much longer distance to stop than a slow one. The joule is the SI unit of energy and equals one newton metre; one joule is the work done when a force of one newton moves a body through one metre. Option B is wrong because 110 J is mass multiplied by speed, which gives momentum, not energy, and in different units. Option C is wrong because 1100 J leaves out the half in the formula, that is it works out m v squared. Option D is wrong because 2750 J is ten times the correct value. Exam tip: write half m v squared carefully, because the half and the squared speed are where marks are usually lost.
Practice Questions
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- B.Martin Luther
- C.Johannes Kepler
- D.Copernicus
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- C.Urea is produced from digestion of starch.
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- 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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- 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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