QJEEAdv08Phd1a9: JEE Advanced 2008 Physics - Class 11 JEEAdv08Phd1a9 Solution: STATEMENT 1 : It is easier to pull a heavy object than to push…

Case I : Free body diagram.

Frictional force ( $fr$ ) = $\mu$ N

Normal force (N) = N $_1$ + $mg$

Frictional force ( $fr$ ) $_\mathrm{I}$ = $\mu$ (N $_1$ + $mg$ ) ..... (i)

Where N = Normal force

$\mu$ = Coefficient of friction

$m$ = mass of object

$g$ = acc. due to gravity

N $_1$ = Normal force i.e., vertical component of force due to push.

N $_2$ = Parallel component of force due to push.

Case II : Free body diagram (Pull)

For balancing the force,

N = N $_1$ $-$ $mg$

Frictional force $(fr)$ $_\mathrm{II}$ = $\mu$ N ..... (ii)

From eq. (i) and (ii)

$(fr)$ $_\mathrm{I}$ > $(fr)$ $_\mathrm{II}$

In case of pull, it is easy to move object.

Statement 1 is true. Statement 2 is true.

Force of friction depends on roughness of two surfaces in contact. If roughness will increase, the force of friction will also increase.