Find the coefficient of kinetic friction between a 3.85-kg block and the horizontal surface on which it rests if an 850-N/m spring must be stretched by 6.20 cm to pull it with constant speed. Assume that the spring pulls in the horizontal direction.

Solution 71GP

Step 1 of 3</p>

Here we have to calculate the coefficient of kinetic friction between the given block and the horizontal surface on which it is at rest.

In the given case, a block of lies on a horizontal plane with kinetic friction . If a spring with spring constant is stretched to a length to pull the block with constant speed by assuming all the pulls are in horizontal direction.

Step 2 of 3</p>

Here let us consider the motion of the block is along x-axis which is horizontal direction.

Since the block moves with constant speed, the acceleration of the block will be zero (a=0). Therefore, the net force acting on the block will be zero.

Considering the horizontal components acting on the block, we can write

Using and where N is the normal force on block, we get

Solving for ,

Also normal force is given by considering vertical components , that is