The direction of acceleration in uniform circular motion is along the
- A.direction of motion.
- B.tangent to the circle at the point of observation.
- C.direction of velocity.
- D.direction perpendicular to velocity.
Correct answer
Explanation
The correct answer is D, direction perpendicular to velocity. In uniform circular motion the acceleration points towards the centre of the circle, at right angles to the velocity.
In uniform circular motion the speed stays the same, but the direction of motion changes at every point, so the velocity keeps changing and the body is accelerating. This centripetal acceleration has the size v²/r, where v is the speed and r the radius, and it always points along the radius towards the centre. Because it is at right angles to the motion, it changes only the direction of the velocity, not its size. The force behind it, the centripetal force, comes from tension in a string, friction on a road or gravity for a satellite.
Option A is wrong because the direction of motion is along the tangent, and an acceleration along it would change the speed. Option B is wrong because the tangent is the direction of the velocity, not of the acceleration. Option C is wrong for the same reason.
Exam tip: uniform circular motion: velocity along the tangent, acceleration towards the centre, magnitude v²/r.
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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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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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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