Question

A block of mass $m$ is placed on a weighing machine and it is also attached to a spring balance. The whole system is placed in a lift as shown in figure. Lift is moving with constant acceleration $10m/s^2$ in upward direction. The reading of the weighing machine is $500N$ and the reading of spring balance is $300N$. Find the actual mass of the block in kg. Take $g=10m/s^2$.

• A. 30
• B. 40
• C. 50
• D. 80

Answer 1

The correct option is B 40

m $=$ mass of the block
Applying Newton's Law on the block in vertical direction
T + N - mg $=$ma ...........(1)
T $=$ 300 N (given reading of spring balance)
N $=$ 500 N (given reading of W.M.)
a $=$ $10m/s^2$
$m=\frac{T+N}{g+a}=\frac{500+300}{20}kg=$ 40 kg