We are learning Newton laws in the University and were given the following problem: In the system described in the image, the man is pulling two massless ropes with a force of $F$ each. We are required to calculate the acceleration of the system.
Given $m_1$ - mass of the man, $m_2$ - mass of the platform, I thought the solution will simply be: $$ (m_1 + m_2)a = -(m_1 + m_2)g + 2F \rightarrow a = \frac{2F}{(m_1 + m_2)} - g $$
But apparently the answer is: $$ a = \frac{4F}{(m_1 + m_2)} - g $$
And I can't quite wrap my head around how the force the man put essentially "doubled". I was given an answer of how the tension in the rope needs to be uniform through the entire rope - so with accordance with Newton second law each rope is pulling the man upwards in equal force, but also the bottom of the rope pulls up the platform in an equal force, so it adds up to $4F$.
I was hoping you could help me make sense of this problem because it doesn't sit well with me.