An overview of the concepts of Work Done,Energy and Power

1. Topic 2 – Mechanics 2.3 – Work, Energy and Power

3. Physical work clearly depends on the force used to do that work.

4. Joule's insight was to say simply that the only factors affecting the amount of work done are the size of the force, and how far the object is moved in the direction of the force .

6. F is the force applied in newtons (N)

7. s is the displacement in (m)

9. Lifting a 20kg box up on to a shelf 2m high.

12. 30 o to the horizontal

19. Absolute Gravitational Potential Energy is a relative quantity and is defined as being zero at infinity (see Unit 6.1)

20. In all real-world situations we are able to define our own “zero” and so work with Change in gravitational Potential Energy.

22. If working in a situation where g is variable, then a graph is generally used to find the area gh.

25. Radiant – energy carried by em waves

26. Internal – energy of molecular vibrations / motions.

28. Electrostatic Potential – energy stored in an electrical field.

29. Elastic Potential - energy stored in stressed inter-molecular bonds.

30. Chemical Potential – energy stored in intra-molecular bonds

33. Through Work done by a force

34. Through Heating due to a temperature difference.

37. The speed of the ball at the bottom of the ramp

38. The average value of the friction force of the sand.

42. In all collisions and explosions momentum is conserved if no external force acts.

43. In elastic collisions the total kinetic energy of the system is also conserved.

44. In inelastic collisions the total kinetic energy is not conserved; some energy will be transferred to sound, internal energy or stored as elastic energy.

45. In an explosion , the total momentum is always zero.