A rough vertical board has an acceleration d so that a 2 kg block pressing against it does not fall. The coefficient of friction between the block and the board should be

Question

A rough vertical board has an acceleration d so that a 2 kg block pressing against it does not fall. The coefficient of friction between the block and the board should be (A)  >g/a  (B)  < g/a  (C)  =g/a  (D)  >a/g

Tardigrade Admin · Accepted Answer

For the limiting condition upward friction force between board and block will balance the weight of the block, <img class="img-fluid question-image" alt="image" src="https://cdn.tardigrade.in/img/question/physics/491bb9804fdb0f4f8607d50ec5ae11a6-.png" /> ie, F>m g ⇒ μ R>m g ⇒ μ(m a)>m g ⇒ μ>(g/a)

Q. A rough vertical board has an acceleration $d$ so that a $2 k g$ block pressing against it does not fall. The coefficient of friction between the block and the board should be

$> g / a$

$< g / a$

$= g / a$

$> a / g$

For the limiting condition upward friction force between board and block will balance the weight of the block,

ie, $F > m g$
$\Rightarrow μ R > m g$
$\Rightarrow μ (ma) > m g$
$\Rightarrow μ > \frac{g}{a}$

Q. A rough vertical board has an acceleration d so that a 2kg block pressing against it does not fall. The coefficient of friction between the block and the board should be

>g/a

<g/a

=g/a

>a/g