Question

In Fig., block 1 is placed on top of block 2. Both of them have a mass of 1 kg. The coefficient of friction between blocks 1 and 2 are ${\mu }_s$ = 0.75 and ${\mu }_k$ = 0.60.
The table is frictionless. A force P/2 is applied on block 1 to the left, and force P on block 2 to the right. Find the minimum value of P such that sliding occurs between the two blocks.

Answer 1

For Block $1$ to now

$P/2\ge 6$

$P\ge 12⟶\left(1\right)$

For block $\left(2\right)$ to move

$P\ge 6\to \left(2\right)$

From $\left(1\right)$ and $\left(2\right)$ we conclude that the block will slide

if $P\ge 6$.