If the elevated end of the plank is raised, the acceleration of the trunk will increase. This is because the raised end of the plank increases the angle of inclination of the plank, which results in a greater component of the gravitational force acting parallel to the plank.
As a result, there is an increase in the net force acting on the trunk, which in turn increases its acceleration. This is described by the formula:
a = g × sinθ
where "a" is the acceleration of the trunk, "g" is the acceleration due to gravity, and θ is the angle of inclination of the plank.
By raising the elevated end of the plank, the angle of inclination (θ) increases, which results in an increase in the sinθ value, and, therefore, an increase in the acceleration (a).