HELP ASAP ! Which of the following situations would result in no work done by the force indicated?

a
The object undergoes only a slight displacement while the force is acting on it.
b
The force is perpendicular to the displacement of the object.
c
The force is not completely parallel to the displacement of the object
d
All of the above result in no work done by the force indicated.

b  The force is perpendicular to the displacement of the object.

Explanation:

Work is done when a force is applied on a body causing it to move in a particular direction.

  Work done  = Force x displacement

For work to be done, a force must applied on a body to move it through a specific distance in direction.

When force is perpendicular to the displacement of the object, the component vector resolution is 0 and the work done is 0.

air exerts forces on falling objects near earth’s surface.

explanation:

the term 'free falls' refer to object that are falling towards the earth, in a situation in which gravity is the only force acting on the object.

for an object in free fall, the acceleration is constant (g, the gravitational acceleration), and so the velocity of the object constantly increases.

for objects near earth's surface, there is always another force acting on the object: the resistance due to the air. this force is opposed to the direction of fall of the object, and it is proportional to the velocity of the object, so as the object falls down, this force increases up to a point when it balances the force of gravity, and the object continues its motion at constant velocity (called terminal velocity). since in this case gravity is not the only force acting on the object, we are not in a situation of free fall.