This is a common Physics paradox:

The paradox:

A donkey starts to pull a cart (he exerts a force in one direction). The cart therefore exerts the same amount of force on the donkey (a force in the opposite direction). (Newton's third law: For every action, there is an equal and opposite reaction.) So how can the donkey pull the cart if the cart exerts the same amount of force on the donkey in the opposite direction? Should he not move?

This is not a paradox. It's a misapplication of Newton's 3rd law.

Newtons 2nd Law says that an object of mass

m, acted upon by a net force

F, experiences an acceleration

a,

in the direction of F, such that

F=ma. The cart accelerates because it experiences an imbalance of forces.

Newton's 3rd law is different.

It does not apply to an object.It does not say that the vector sum of the forces acting upon an object is zero.

It says that at the

interface between two objects, equal and opposite forces are exerted.

The ground, the donkey and its harness all combine to exert an unopposed force to the cart, so it accelerates.

That happens because these objects are in contact, and Newton's 3rd law is obeyed at these points of contact.

Take a baseball hit by Alex Rodriguez's bat. Ball and bat exert equal and opposite forces on each other

[N3].

No other force acts on the ball, so the ball accelerates.

[N2]Because the ball exerts an equal force on the bat

[N3], the bat slows down

[N2].

The motion of objects does not contradict a right application of Newton's 3rd law.