(UNICESUMAR 2015) - Question Medium of Physics

The city of Salvador, famous for its hills and elevators, is a perfect example to demonstrate the force of traction. The Lacerda Elevator, one of the main postcards of the city, transports thousands of people daily between the Upper Town and the Lower Town. Suppose one day, a group of 15 people with an average mass of 70kg decide to use the elevator at the same time. Considering the elevator's mass as 500kg and the acceleration due to gravity equal to 10 m/s², what would be the traction force on the elevator cable when it is at rest or moving at a constant speed?

A technician from an electronics company is working on a circuit involving three capacitors in series. The capacitors have capacitances of 6μF, 8μF, and 12μF, respectively. Assuming the potential difference applied to the capacitors is 60V, determine the charge stored in each capacitor and the equivalent capacitance of the series configuration.

A motor operates according to the Carnot cycle between two thermal sources. The hot source is at a temperature of 500 K and the cold source at 300 K. Determine the efficiency of the motor, knowing that the efficiency of the Carnot cycle is calculated by the expression 1 - (Tcold/Thot), where Tcold and Thot are the temperatures of the cold and hot sources, respectively. Discuss briefly the importance of the maximum efficiency of the Carnot cycle in practical applications of thermal engines.