# Relation Between Distributed Load and Shear

I saw the following extract from Hibbeler's 'Mechanical Engineering - Statics, 13th Ed';

The general result $\frac{dV}{dx} = w(x)$ seems to rely on the shear forces at the interface acting in opposite directions. If my force distribution function along the top of the beam is linear with gradient 0, then my $\Delta F$ would act in the centre of $\Delta x$ and the shear force at the right and left interface of $\Delta x$ would be identical vectors, both acting downwards. My vertical force equilibrium would then be described as follows; $$\Delta F - V - (V + \Delta V)=0$$

This then breaks the general relationship described by (7-1). What am I misunderstanding?