$F=ma$. A car strikes a wall at 60 mph. Its acceleration is zero at the time. The force of the car against the wall or vice versa is? To look at the car the force is not zero. Please explain.
The minute the car touches the wall, it will decelerate rapidly (and crumple in the process). This deceleration/crumpling will be from the force the wall exerts on the car, which can be calculated from $F=ma$.
The car also exerts a force on the wall. However, the wall is attached to the ground, and the ground exerts a balancing force on the wall, keeping it in place. This means that the wall exerts an equal and opposite force on the ground. But, the ground (Earth) is so massive that we can just assume that the mass is infinite, giving us zero acceleration for the ground.