Introduction:
When an object is in motion or about to be set in motion, the force of static friction comes into play. Static friction is the force that prevents the object from sliding or moving when a force is applied to it. As the object starts to move, the static friction decreases and is replaced by kinetic friction. The work done by friction is the product of the force of friction and the displacement of the object.

Explanation:
The work done by static friction on an object can be positive, negative, or zero, depending on the scenario. Let's discuss each possibility:

1. Positive work:
When an external force is applied to an object in the direction of motion, and the force of static friction opposes this motion, the work done by static friction is positive. In this case, the object is moving in the same direction as the force of friction, and the frictional force helps in increasing the object's kinetic energy. For example, when a car accelerates forward, the static friction between the tires and the road does positive work on the car.

2. Negative work:
If the external force applied to the object is in the opposite direction of motion, the work done by static friction is negative. The frictional force opposes the motion and does negative work, decreasing the object's kinetic energy. For instance, when a car decelerates, the static friction between the tires and the road does negative work on the car.

3. Zero work:
In some cases, the object does not move even when an external force is applied. In such situations, the work done by static friction is zero. This occurs when the applied force is balanced by the static frictional force, and the object remains at rest. For example, if you push a wall with all your strength, the wall does not move, and therefore, the work done by static friction is zero.

Conclusion:
The work done by static friction on an object can be positive, negative, or zero, depending on the direction of the external force applied and the resulting motion of the object. It is essential to consider the specific scenario to determine the sign and value of the work done by static friction.