Question

Two blocks of masses 40 kg and 20 kg are connected by a wire that has a linear mass density of 1 g/m. These blocks are being pulled across horizontal frictionless floor by horizontal force F that is applied to 20 kg block. A transverse wave travels on the wave between the blocks with a speed of 400 m/s (relative to the wire). The mass of the wire is negligible compared to the mass of the blocks. The magnitude of F is

• A. 160 N
• B. 240 N
• C. 320 N
• D. 400 N

Answer 1

The correct option is B

240 N

Tension T in the wire $=v^2\mu =(400{)}^2\times {10}^{-3}=160N$ Force applied

$F=\frac{T(m_1+m_2)}{m_1}$

$=160\times \frac{(40+20)}{40}=240N$