Lesson 6 - Forces Work and Power

• What is the aim of the course "Science for engineers - 102"?

  Understand fundamental scientific principles of mechanical engineering
• What are the types of energy stores mentioned?

  • Potential Energy
  • Kinetic Energy
  • Elastic Potential
  • Nuclear Potential
• What is gravitational potential energy stored due to?

  Position relative to a reference level
• What is elastic potential energy stored in?

  Objects that have been stretched or compressed
• What is nuclear potential energy stored within?

  The nucleus of an atom
• What is mechanical energy composed of?

  • Kinetic Energy
  • Potential Energy
• What happens to mechanical energy when there is little resistance?

  It is maintained in the system
• How does friction and drag affect mechanical energy?

  They remove mechanical energy by causing heating
• What is internal energy associated with?

  Random disordered motion of molecules
• Does a glass of water sitting on a table have energy?

  Yes, it has microscopic kinetic energy
• What is the symbol commonly used for internal energy?

  U
• What happens to mechanical energy if there are no collisions?

  It has no effect on internal energy
• What are the equations for kinetic energy and gravitational potential energy?

  • Kinetic Energy: $KE =$$\frac{1}{2} m v^2$
  • Gravitational Potential Energy: $GPE =$$mgh$
• What does the variable 'm' represent in the kinetic energy equation?

  Mass in kilograms
• What does the variable 'v' represent in the kinetic energy equation?

  Velocity in meters per second
• What does the variable 'g' represent in the gravitational potential energy equation?

  Gravitational field strength
• What does the variable 'h' represent in the gravitational potential energy equation?

  Height in meters
• What are the four ways to transfer energy?

  1. Radiant
  2. Heat
  3. Electricity
  4. Force
• Can we consider work is done during radiant energy transfer?

  No, EM waves don't move particles
• Can we consider work is done during heat transfer?

  No, particles return to original position
• Can we consider work is done during electricity transfer?

  Yes, it involves displacement
• Can we consider work is done during force transfer?

  Yes, a force must be applied
• What does friction do in terms of energy transfer?

  Transfers energy to internal energy store
• What is the definition of mechanical power?

  Rate of energy transfer in a system
• What is the formula for mechanical power?

  $P =$$\frac{w}{t}$
• What is the unit of power?

  Watt (W)
• How is efficiency defined?

  Ratio of output work to input work
• What is the formula for efficiency?

  $\eta =$$\frac{useful}{input} \times 100$
• What does an efficiency of less than 100% indicate?

  Losses between input and output work
• What does the principle of conservation of energy state?

  Energy can never be created or destroyed
• What happens to energy in a system?

  • Energy is transferred from one store to another
  • Energy can be transferred from one place to another