When the weigth of a body placed on a surface is doubled, how does the coefficient of friction channge ?

When normal reaction is halved the coefficient of friction is

In the figure, a block of weight 60 N is placed on a rough surface. The coefficient of friction between the block and the surface is 0.5. The minimum weight of the block does not slip on the surface is (x xx 10) N. The value of x is

A block of mass M is being pulley along horizontal surface .The coefficient of friction the block and the surface is mu If another block of mass M//2 is placed on the block and it is pulled is again pulled on the surface , the coefficient of friction the block and the surface will be

A body slides down a rough inclined plane and then over a rough plane surface. It starts at A and stops at D. The coefficient of friction is :

A uniform chain is placed at rest on a rough surface of base length l and height h on an irregular surface as shown in figure Then the minimum coefficient of friction between the chain and the surface must be equal to

A body of mass m is placed on a rough surface with coefficient of friction mu inclined at theta . If the mass is in equilibrium , then

A body of mass m is placed on a rough surface with coefficient of friction mu inclined at theta . If the mass is in equilibrium , then

In the given situation disc and ring are connected with a string as shown in the figure. Both are placed on the rough surface of coefficient of friction mu . A force F is applied on the centre of disc horizontally. Then frictional force acting on the ring will be

What is the value of applied force ‘F’ which is exerted at an angle theta with the horizontal on a block of mass ‘m’ placed on a horizontal rough surface, if the coefficient of static friction between the block and the surface is , such that the block is on the verge of moving horizontally?

A ring of radius R is first rotated with an angular velocity omega and then carefully placed on a rough horizontal surface. The coefficient of friction between the surface and the ring is mu . Time after which its angular speed is reduced to half is