Question

In the figure given below, the magnitude of normal reaction exerted by the floor on the 50 kg block is [The string and pulley are massless and all the surfaces are smooth] [Take $g=10m/s^2$]

• A. 200 N
• B. 300 N
• C. 700 N
• D. 500 N

Answer 1

The correct option is B 300 N

Let T be the tension in the string and R be the normal reaction force on the block of mass 50 kg applied by the floor.
$m_1=50kg$
$m_2=20kg$
For the block of mass $m_2$ (20 kg):
At equilibrium, $T=m_{2}g=20g$
For the block of mass $m_1$ (50 kg):
$T+R=m_{1}g$
$\Rightarrow R=m_{1}g–T$
$\Rightarrow R=50g–20g=30g$
$\Rightarrow R=300N$ $(\because g=10m/s^2)$
Hence, the correct answer is option (1).