Calculate the acceleration of the block and trolly system shown in the figure. The coefficient of kinetic friction between the trolly and the surface is \(0.05.\) 
( \(g=10~\text{m/s}^2,\) the mass of the string is negligible and no other friction exists)

See the figure given below, a mass of \(4~\text{kg}\) rests on a horizontal plane. The plane is gradually inclined until at an angle \(\theta=15^\circ\) with the horizontal, the mass just begins to slide. What is the coefficient of static friction between the block and the surface?

 
1. \(0.27\)
2. \(0.53\)
3. \(0.23\)
4. \(0.25\)