JEE Main 2022 · 29 Jul · Shift 1 · Physics Q37

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PhysicsSingle correct+4 / -1Question 37 of 90

Given below are two statements : One is labelled as Assertion (A) and the other is labelled as Reason (R).

Assertion (A) : Clothes containing oil or grease stains cannot be cleaned by water wash.

Reason (R) : Because the angle of contact between the oil/grease and water is obtuse.

In the light of the above statements, choose the correct answer from the option given below.

Both (A) and (R) are true and (R) is the correct explanation of (A)

Both (A) and (R) are true but (R) is not the correct explanation of (A)

(A) is true but (R) is false

(A) is false but (R) is true

Answer and worked solution

Official answer: A

Wetting. Water makes an obtuse contact angle with oil or grease, so it does not wet or lift the stain; that is why detergents are needed. Both are true and R explains A.

(A)

Topics:Surface tension

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JEE Main 2022 · 29 Jul · Shift 1, Physics question 37