Answer
The work done by the force of gravity is negative in the half-circle in which the plane is gaining height, while it is positive when the plane is going down.
The work is NOT constant.
When the plane is flying perpendicularly upwards, work is negative and its magnitude is maximum.
When the plane is flying perpendicularly downwards, work is positive and its magnitude is maximum.
And when the plane is parallel to the ground, i.e. at the bottom and top of the circle, the work done by gravity is zero.
Work Step by Step
The work done by the force of gravity is negative in the half-circle in which the plane is gaining height, while it is positive when the plane is going down.
The work is NOT constant.
When the plane is flying perpendicularly upwards, work is negative and its magnitude is maximum.
When the plane is flying perpendicularly downwards, work is positive and its magnitude is maximum.
And when the plane is parallel to the ground, i.e. at the bottom and top of the circle, the work done by gravity is zero.
