Question

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. If both Assertion and Reason are true and the Reason is correct explanation of the Assertion.
B. If both Assertion and Reason are true and the Reason is not the correct explanation of the Assertion.
C. If Assertion is true, but the Reason is false
D. If Assertion is false but the Reason is true.

Answer 1

Correct Answer - C
Decrease in mechanical energy in first
`= E_(i)-E_(f) =1/2mv^(2)-0`
`=1/2mv^(2)`
Decrease in mechanical energy in second
`=E_(i)-E_(f) =1/2mv^(2)-mgh`.