Is it possible for a frictional force to increase the mechanical energy of a system? If so, give examples.
No, it is not possible for a frictional force to increase the mechanical energy of a system. In fact, friction always opposes the motion of objects and acts to decrease the mechanical energy of a system.
To understand why, let's first define mechanical energy. Mechanical energy is the sum of kinetic energy (energy of motion) and potential energy (energy stored in an object due to its position). Friction generates heat, which is a form of energy, but it does not contribute to the mechanical energy of the system.
When an object moves against a frictional force, such as pushing a block along a rough surface, the work done by the external force is partially used to overcome friction. This work is converted into heat energy, which is dissipated into the surroundings. As a result, the mechanical energy of the system decreases.
Examples of situations where friction decreases the mechanical energy include:
1. Sliding a book on a table: As you exert a force to slide the book across the table, friction opposes the motion and converts some of the kinetic energy into heat.
2. Braking a car: When you apply the brakes in a car, the friction between the brake pads and the rotating wheels slows down the car by converting its kinetic energy into heat.
It is important to note that while friction decreases the mechanical energy of a system, it is an essential force in many everyday activities and plays a critical role in preventing objects from sliding uncontrollably and causing accidents.