Final answer:
Centripetal force is the net force on an object in circular motion directed towards the center, and it can come from tension, gravity, or other forces. Tension must be equal or greater than gravity if it provides additional force needed for centripetal acceleration. The correct answer is that tension is greater than gravity.
Step-by-step explanation:
Tension and Centripetal Force
Centripetal force is the net force that acts on an object moving in a circular path, directed towards the center of the circle. Any type of force, like tension, gravitational force, friction, etc., can act as a centripetal force or in combination as long as it is directed towards the center of the circle. Furthermore, the centripetal force can sometimes be the result of both gravitational force and tension, such as in the case of a tetherball moving in a circular path.
For an object in circular motion, the net force must be the centripetal force required to maintain the motion. Applying Newton's second law, we can deduce that the net force is the sum of all individual forces. If an object is in equilibrium, like a mass hanging from a rope, the tension in the rope is equal to the weight of the object (F = mg). If the object is moving and gravity is also acting on it (such as a pendulum or a satellite in orbit), tension may be greater than gravity to provide the additional force needed for centripetal acceleration, or gravity may be greater than tension if it's the dominant force providing the centripetal force (e.g., planets orbiting the sun).
The correct answer to the original question ("Tension and gravity (net force) is the centripetal force when..."), given the provided information, is b) Tension is greater than gravity.