The centripetal acceleration of a body moving in a circle of radius r with uniform speed v is directed:
- A.Along the tangent, in the direction of motion
- B.Towards the centre of the circle
- C.Away from the centre of the circle
- D.Vertically downward
Correct answer
Explanation
The correct answer is B, towards the centre of the circle. In uniform circular motion the magnitude of the velocity does not change, so the acceleration can have no component along the direction of motion; the whole of it is perpendicular to the velocity and points to the centre, which is why it is called centripetal, meaning centre seeking, and its magnitude is the square of the speed divided by the radius. Option A is wrong because a tangential acceleration would change the speed, which uniform circular motion does not. Option C describes the direction of the centrifugal force, a pseudo force that appears only when the motion is described from the rotating frame, and it is not the direction of the real acceleration. Option D is true only in free fall under gravity; for a satellite the gravitational pull happens to be the centripetal force, but it points to the centre of the earth and not simply downward in the local sense.
Read the full article: Friction and Circular Motion: Laws, Formulas and PYQs
Practice Questions
View allWhen a force resists the relative motion between two surfaces, it is called _______
- A.Resistance
- B.Convection
- C.Friction
- D.Induction
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Friction is defined as the force that opposes the relative motion, or the tendency of relative motion, between two surfaces in contact; it acts along the surfaces and always against the direction of motion.
Read the full explanation →Which of the following statements about the coefficient of friction is correct?
- A.It is measured in newton
- B.It has no unit and no dimensions
- C.It is measured in newton per square metre
- D.It is measured in joule
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The coefficient of friction is the ratio of the limiting or kinetic frictional force to the normal reaction, and since both are forces the ratio is a pure number; the same reasoning applies to other ratios such as the refractive index and relative density.
Read the full explanation →For the same pair of surfaces, which of the following types of friction is the smallest?
- A.Static friction
- B.Limiting friction
- C.Sliding friction
- D.Rolling friction
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When a body rolls, the surfaces in contact change continuously and the irregularities have no time to interlock deeply, so rolling friction is very much smaller than sliding friction; this single fact is the reason the wheel was invented and the reason a ball bearing is fitted wherever a shaft…
Read the full explanation →In uniform circular motion, which of the following quantities remains constant?
- A.Velocity
- B.Speed
- C.Acceleration
- D.Linear momentum
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In uniform circular motion the body covers equal arcs in equal times, so its speed, a scalar, does not change; its kinetic energy and its angular velocity are constant too.
Read the full explanation →A body of mass 5 kg is rotating with angular velocity 10 rad/s in a circular path of radius 0.1 m. Determine the centrifugal force acting on the body.
- A.100 N
- B.50 N
- C.80 N
- D.60 N
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The centrifugal force has the same magnitude as the centripetal force, which for a body moving in a circle is the mass multiplied by the square of the angular velocity multiplied by the radius.
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