Question

On a smooth plane surface (figure) two block $A$ and $B$ are accelerated by applying a force $15\text{N}$ on $A$. If mass of $B$ is twice that of $A$, then net force on $B$ is

• A. $30\text{N}$
• B. $15\text{N}$
• C. $10\text{N}$
• D. $5\text{N}$

Answer 1

The correct option is C $10\text{N}$

Let $x$ be the mass of A then mass of B will be $2x$
Since the force on the combined system if $15\text{N}$ and the total mass of the combined system is $3x$
The acceleration of both the blocks =
$\frac{15}{3x}=\frac{5}{x}$
Applying Newton's second law for block B
$\therefore$ Force on $B=\frac{5}{x}\times 2x=10\text{N}$