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Asseration : A block of mass m starts mo...

Asseration : A block of mass m starts moving on a rough horizontal surface with a velocity v. It stops due to friction between the block and the surface after moving through a ceratin distance. The surface is now tilted to an angle of `30^@` with the horizontal and same block is made to go up on the surface with the same initial velocity v. The decrease in the mechanical energy in the second situation is small than the first situation.
Reason : The coefficient of friction between the block and the surface decreases with the increase in the angle of inclination.

A

(a) Statement I is true, Statement II is true, Statement II is a correct explanation for Statement I.

B

(b) Statement I is true, Statement II is true, Statement II is not a correct explanation for Statement I.

C

(c) Statement I is true, Statement II is false.

D

(d) Statement I is false, Statement II is true.

Text Solution

Verified by Experts

The correct Answer is:
C
Decrease in mechanical energy in case I will be
`DeltaU_1=1/2mv^2`
But decrease in mechanical energy in case II will be
`DeltaU_2=1/2mv^2-mgh`
`:. DeltaU_2ltDeltaU_1`
Hence, Statement 1 is correct. More ones, statement 2 is wiring.
Therefore, option (c) is correct.
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