After a long night of cramming for a test, your college room-mate hits his head forcefully against the wall of your room in despair. According to Newton’s 3rd Law, as he exerts a force against the wall, there must be an equal and opposite force. How does that opposite force show itself in this case?

the wall contracts the force exerted by his head. The wall produces the opposite force which is equal to the force his head bangs the wall with.

Explanation: if his head exerts a much greater force than the wall can counteract the wall will be destroyed, if the wall exerts a much greater force than his head exerts he will be pushed far back and might even suffer a broken head.

The wall in this case provides the opposite reactive force.

it takes about 30 days for it to break down

the answer is c. the lower legs are levers, and the knees are fulcrums. the ankles hold the loads.