Answer:
Equal (and the direction is opposite)
Explanation:
Newton's third law of motion states that:
"when an object A exerts a force on an object B, object B exerts an equal and opposite force on object A. The two forces are called action and reaction"
In this situation, we have a hammer exerting a force on a nail. We can think the hammer as object A and the nail as object B, so according to Newton's third law, the nail must exert an equal and opposite force on the hammer.
Therefore, the magnitude of the force that the nail exerts on the hammer is equal to the force exerted by the hammer on the nail (and in opposite direction)
