Question

A body weighing 300 N is resting on a rough horizontal table. A pull of 100 N applied at an angle of 15 degree with the horizontal just causes the body to slide over the table. Make calculations for the normal reaction and the coefficient of friction.​

Answer 1

Given:

A body weighing 300 N is resting on a rough horizontal table. A pull of 100 N applied at an angle of 15 degree with the horizontal just causes the body to slide over the table.

To find:

• Normal reaction ?
• Coefficient of friction ?

Calculation:

Let normal reaction be N :

$\therefore \: N = mg - 100 \sin( {15}^{ \circ} )$

$\implies\: N = 300 - 100 \sin( {15}^{ \circ} )$

$\implies\: N \approx 300 - 25$

$\implies\: N \approx 275 \: Newton$

So, normal reaction is 275 Newton.

$\therefore \: f \cos( {15}^{ \circ} ) = \mu N$

$\implies \: 100 \cos( {15}^{ \circ} ) = \mu \times 275$

$\implies \: 96= \mu \times 275$

$\implies \: \mu = \dfrac{96}{275}$

$\implies \: \mu = 0.34$

So, coefficient of friction is 0.34