Question

The model airplane has a mass of 0.90 kg and moves at constant speed of 19 m/s on a circle that is parallel to the ground. The path of the airplane and the guideline lie in the same horizontal plane because the weight of the plane is balanced by the lift generated by its wings. What is the work done by the tension in the 17 m guideline when the model airplane completes one circle?

Answer 1

The work done by any force is calculated as the dot product of the force and the displacement of its point of application.

Thus the work done by a force is zero when :

a) The magnitude of displacement of point of application of force is zero.

B) The angle between the force and the displacement is 90 degrees

The work done by the tension (which acts as the centripetal force responsible for the circular motion of model airplane in the horizontal plane) is ZERO because

A) The tension force is always at 90 degree to the velocity of the plane (hence also its displacement)

B) the displacement of the plane in a full circle is zero.