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
Correct answer
Explanation
The correct answer is B, it has no unit and no dimensions. 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. Option A is wrong because newton is the unit of force itself, and the frictional force, not the coefficient, is measured in it. Option C is wrong because newton per square metre is the pascal, the unit of pressure or stress, which is force divided by area. Option D is wrong because the joule is the unit of work and energy, a force multiplied by a distance. Remember also that the coefficient of static friction is larger than the coefficient of kinetic friction for the same pair of surfaces.
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 →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.
Read the full explanation →A car travels in a circular motion. Which of the following statements is true?
- A.Distance travelled by the car will always be less than displacement of the car.
- B.Distance travelled by the car will always be more than displacement of the car.
- C.Distance travelled by the car will always be equal to displacement of the car.
- D.Distance travelled by the car will be zero when displacement is zero.
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Distance is the length of the actual path and displacement is the straight line from the start to the finish, so on a curved path the two can never be equal: the arc of a circle is always longer than the chord joining its ends.
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