Final answer:
3. Friction decreases the kinetic energy of an object by converting it into other forms, such as heat and sound, thus opposing motion and providing a means to stop moving objects efficiently.
Step-by-step explanation:
When work is done on an object, there can be a change in its kinetic energy. Regarding the effect of friction on the kinetic energy of an object, friction generally decreases the kinetic energy of the object by converting it into other forms of energy, typically heat and sometimes sound. For instance, when you apply the brakes in a car, the kinetic energy of the moving car is reduced due to the work done by the friction between the brake pads and the wheels. As per the work-energy theorem, the work done by friction is negative, since friction is in the opposite direction of motion, which leads to a decrease in the kinetic energy of the object.
Friction plays a critical role in everyday activities, like walking or driving a car. Without friction, we would not be able to bring moving objects to a stop efficiently, but at the same time, it is the force that opposes motion and thus drains energy from the system. Such effects of friction are fundamentally important in understanding energy conservation and energy transformations in physics.