Question

In a laboratory experiment on friction, a block of weight $135N$ lying on a rough horizontal table is pulled by a horizontal wire. The pull $\left(P\right)$ gradually increases until the block begins to move and continues to increase thereafter. Given figure shows a graph of the friction force $\left(f\right)$ on this block as a function of the pull $\left(P\right)$


The region of the graph where kinetic friction occur is

• A. $P<50N$
• B. $P>75N$
• C. $P=0N$
• D. $P<75N$

Answer 1

The correct option is B $P>75N$

If applied force keeps on increasing suddenly the object starts moving and the value of resisting friction force decreases and continues with a constant value of friction, at this stage it is known as Kinetic friction. Kinetic friction has a constant value but little less than Limiting friction. Kinetic friction occurs when an object is in motion and it has a constant value as shown in the given graph. Kinetic friction starts acting from $P<75N$ i.e. option $\left(2\right)$