Question

What is the reading of the spring balance in the following device?

• A. $\frac{20}{3}\text{kg}$
• B. $\frac{40}{3}\text{kg}$
• C. $\frac{10}{3}\text{kg}$
• D. $\frac{1.5}{3}\text{kg}$

Answer 1

The correct option is B $\frac{40}{3}\text{kg}$

Let $T$ be the reading of the spring balance. Then for $20\text{kg}$ block:$\text{20g - T = 20a}$.......(i)
For $10\text{kg}$ block :$\text{T - 10g = 10a}$ .....(ii)
Solving equations (i) and (ii), we get $a=\frac{g}{3},T=\frac{40g}{3}$
So, the spring balance reading is $\frac{40}{3}\text{kg}$.