Question

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

• A. 30 N
• B. 15 N
• C. 10 N
• D. 5 N

Answer 1

Answer: (C)

Let the mass of block $A$ be $x$ then mass of block $B$ is $2 x$
now consider both box as one system and calculate the acceleration
$a =\frac{15}{3 x }=\frac{5}{ x }$
therefore force on block $B$ is $ma =2 x \times \frac{5}{ x }$
$=10\, N$