When an object is slowing down, the acceleration is in the opposite direction as the velocity.
Assuming negligible air resistance, the shell travels at a constant horizontal velocity equal to what it had immediately after leaving the barrel. The shell is in the air until hitting the target; the length of this period of time is therefore directly proportional to the distance between the barrel and the target.
The shell hits the target below where it was aimed at for it experiences gravitational pull during its flight. With the barrel pointed "parallel to the ground" the shell shall experience no initial vertical velocity, meaning that it its undergoing a freefall on the vertical direction. and are therefore the respective vertical displacements of the two trials.
The formula below relates the vertical displacement to the gravitational acceleration and the time duration of the freefall :
Let and be the duration of the shell's flight on the first and second trials, respectively; Thus
Work = 25N x 4 meters = 100 J
Differences in elevation are best shown using a topographic map. This is because it uses a large-scale detail representation of the the Earth's relief, mostly by using contour lines. Some traditional definitions show both natural and manmade features, which make it the best map to use when dealing with elevations.