Which of the following is an example of a contact force?Select one:a.gravityb.magnetic forcec.frictiond.electric force

Break Down the Problem

1. Identify the types of forces mentioned in the options.
2. Determine which of these forces requires contact between objects to exert its effect.

Relevant Concepts

• Contact Forces: These are forces that occur between two objects that are in physical contact with each other. Examples include friction, tension, normal force, and applied force.
• Non-contact Forces: These forces act at a distance, meaning they do not require direct contact between objects. Examples include gravitational force, magnetic force, and electric force.

Analysis and Detail

1. Gravity (a): A non-contact force that acts over a distance between two masses.
2. Magnetic Force (b): Also a non-contact force, it acts between magnets or magnetic materials without contact.
3. Friction (c): A contact force that occurs when two surfaces move against each other, opposing relative motion.
4. Electric Force (d): Generally a non-contact force that acts over a distance between charged particles.

Verify and Summarize

Among the given options, friction is the only force that requires direct contact between two surfaces. Gravity, magnetic, and electric forces act at a distance.

Final Answer

The example of a contact force is c. friction.