6 meters is left because you subtract 12 meters from 6
The equation for force is F=ma. Because we have the value of mass (0.42 kg) and the acceleration (14.8 m/s^2), simply plug them into the equation for force to get

The answer is 6.22 N because newtons are the unit used to measure force.
The work performed on an object is the force multiplied by the distance it is moved, provided the movement is parallel to the force. Since that is the case here, we can get the work by W=Fd=1900N x 0.23m = 437J. This energy is used to split the wood.
A.) Each point on a wave front acts as a source of secondary waves.