P. 4148. A sample of ideal gas is taken from state A to state B in two different ways. The two states has the same temperature.
a) First it is compressed adiabatically (AC), and then it is cooled down such that its volume remains constant (CB);
b) First it is heated at constant volume (AD), then it is compressed isobarically (DB).
In which case do we perform less work? At state C or at state D will the temperature of the gas be greater?
P. 4149. A 25 cm-long simple pendulum is hanging vertically inside a small car which is at rest. The mass of the bob is 2 grams, its charge is 5.10-8 coulomb. The vehicle is in uniform electric field, and then it will travel in this field. The electric field points vertically upward and its magnitude is 400 kN/C. The vehicle is started at an acceleration of 4.5 m/s2. Air resistance is negligible.
a) Find the maximum speed of the bob with respect to the vehicle.
b) What must the strength of the cord be in order not to be broken during the motion.