Question

Three blocks of masses m₁ = 10 kg, m₂ = 20 kg are connected by strings on smooth horizontal surface and pulled by a force of 60 N. Find the acceleration of the system and frictions in the string.

Answer 1

All the blocks more with common acceleration a under the force F = 60 N. 

F = (m₁ + m₂ + m₃)a

To determine, T₁ → Free body diagram of mass m₁.

T₁ = m₁a = 10 × 1 = 10 N 

To determine, T₂ – Free body diagram of m₃.

F – T₂ = m₃a 

Solving, we get T₂ = 30 N