Thermodynamics

Thermodynamics States About Energy Conversion Thermodynamics is the branch of science that embodies the principles of energy transformation in macroscopic systems. The general restrictions which experience has shown to apply to all such transformations are known as the laws of thermodynamics. These laws are primitive; they cannot be derived from anything more basic. The first law of thermodynamics states that energy is conserved; that, although it can be altered in form and transferred from one place to another, the total quantity remains constant. Thus, the first law of thermodynamics depends on the concept of energy; but, conversely, energy is an essential thermodynamic function because it allows the first law to be formulated. This coupling is characteristic of the primitive concepts of thermodynamics. The words system and surroundings are similarly coupled. A system is taken to be any object, any quantity of matter, any region, and so on, selected for study and set apart (men

Force Problem

  1. The spring is outstretched when x = 0. If the body moves from the initial position x1 = 100 mm to the final position x2 = 200 mm, (a) determine the work done by the spring on the body and (b) determine the work done on the body by its weight. Answer: (a) U1-2 = - 60 J, (b) U1-2 = 2.35 J
  2. Use the work energy method to develop an expression for the maximum height attained by a projectile that is launched with initial speed vo from ground level. Evaluate your expression for vo = 50 m/s. Assume a constant gravitational acceleration and neglect air resistance.
  3. The small body has a speed va = 5 m/s at point A. neglecting friction, determine its speed vB at point B after it has risen 0.8 m. Is knowledge of the shape of the track necessary? Answer: vB = 3.05 m/s.
  4. In the design of spring bumper for a 1500 kg car, it is desired to bring the car to a stop from a speed of 8 km/h in a diameter equal to 150 mm of spring deformation. Specify the required stiffness h of each of the two spring behind the bumper. The spring are undeformed at the start of impact.
  5. The small collar of mass m is released from rest at A and slides down the curved rod in the vertical plane wit negligible friction. Express the velocity v of the collar as it strikes the base of B in term of the given condition. Answer: v
    √ 2gh
  6. The car is moving with a speed vo = 105 km/h up the 6 percent grade and the driver applies the brakes at point A, causing all wheels to skid. The coefficient of kinetic friction for the rain slicked road is mk = 0.6. determine the stopping distance sAB. Repeat your calculations for the case when the car is moving downhill from B to A. Answer: sAB = 65.8 m, sBA = 80.4 m
  7. The 54 kg of woman jogs up the flight of stairs in 5 seconds. Determine her average power output. 
Other Problem Example: Velocity Problem Solving