The tangent of the angle of repose of a surface is equal to:
- A.The normal reaction
- B.The coefficient of static friction
- C.The weight of the body
- D.The acceleration due to gravity
Correct answer
Explanation
The correct answer is B, the coefficient of static friction. The angle of repose is the angle to which an inclined plane must be tilted before a body resting on it just begins to slide. At that instant the component of the weight along the plane equals the limiting friction, and working the two expressions out leaves the tangent of the angle equal to the coefficient of static friction. The angle of friction, defined from the resultant of the normal reaction and the limiting friction, has the same tangent, so the two angles are numerically equal. Option A is wrong because the normal reaction is a force in newton and cannot equal a dimensionless tangent. Option C is wrong for the same reason, and in fact the angle of repose does not depend on the weight at all, which is why a heavier block slides at the same angle. Option D confuses a tangent with an acceleration.
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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