JEE MainPhysicsLaws of MotionMCQ+4 / −1
Given below are two statements : Statement (I) : The limiting force of static friction depends on the area of contact and independent of materials. Statement (II) : The limiting force of kinetic friction is independent of the area of contact and depends on materials. In the light of the above statements, choose the most appropriate answer from the options given below :
- AStatement I is incorrect but Statement II is correct
- BBoth Statement I and Statement II are correct
- CBoth Statement I and Statement II are incorrect
- DStatement I is correct but Statement II is incorrect
View written solutionFree
Correct answer: A
-
Recall the laws of friction
For dry friction between two surfaces:
- Limiting static friction is
- Kinetic friction is
where:
- are coefficients of friction,
- is the normal reaction.
-
Check Statement (I)
Statement (I): The limiting force of static friction depends on the area of contact and independent of materials.
From we see that limiting static friction:
- is independent of area of contact (for ideal dry surfaces),
- depends on the nature of materials through .
Hence Statement (I) is incorrect.
-
Check Statement (II)
Statement (II): The limiting force of kinetic friction is independent of the area of contact and depends on materials.
Using kinetic friction:
- is independent of area of contact,
- depends on materials through .
Hence Statement (II) is correct.
-
Choose the correct option
Therefore:
- Statement I is incorrect
- Statement II is correct
So the correct option is:
-
Comparison with stored answer
Stored correct answer: A
My derived answer: A
They match.
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