A uniform rope of length l lies on a table. If the coefficient of friction is μ, then the maximum length l₁ of the part of this rope which can overhang from the edge of the table without sliding down is 

1. $\frac{l}{\mu }$

2. $\frac{l}{\mu +l}$

3. $\frac{\mu l}{1+\mu }$

4. $\frac{\mu l}{\mu -1}$

A heavy uniform chain lies on a horizontal table-top. If the coefficient of friction between the chain and table surface is 0.25, then the maximum fraction of length of the chain, that can hang over one edge of the table is 

1. 20%

2. 25%

3. 35%

4. 15%

A uniform chain of length \(L\) hangs partly from a table which is kept in equilibrium by friction. If the maximum length that can be supported without slipping is \(l,\) then the coefficient of friction between the table and the chain is: 
1. \(\frac{l}{L}\)
2. \(\frac{l}{L+l}\)
3. \(\frac{l}{L-l}\)
4. \(\frac{L}{L+l}\)

When two surfaces are coated with a lubricant, then they 

1. Stick to each other

2. Slide upon each other

3. Roll upon each other

4. None of these

A 20 kg block is initially at rest on a rough horizontal surface. A horizontal force of 75 N is required to set the block in motion. After it is in motion, a horizontal force of 60 N is required to keep the block moving with constant speed. The coefficient of static friction is 

1. 0.38

2. 0.44

3. 0.52

4. 0.60