Wpe

question number 13 answer is option 3

@raja
Mechanical energy is conserved
u=0, v=0
mgh(M)mgd=Kf  Ki
=(1/2)mv² (1/2)mu²
=0
So, mgh=Mmgd
M=h/d...... But, we know that h=xsin(theta)
Thus, M=xsin(theta)/d
Where, M=coefficient of friction