A child with mass $20\,\text{kg}$ is standing on the rough top surface of a sledge whose mass is $40\,\text{kg}$. The sledge is able to move along a horizontal surface with no friction. One end of a rope is fixed to the sledge. The rope goes round a stationary frictionless pole, and the child holds the free end of the rope, as illustrated. The rope remains horizontal. The child exerts a horizontal pull of $12\,\text{N}$ on the rope. As a result, the child and the sledge accelerate together with the same acceleration towards the pole. What is the frictional force acting between the child and the sledge?
- A$4.0\,\text{N}$
- B$6.0\,\text{N}$
- C$8.0\,\text{N}$
- D$12\,\text{N}$