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Fisika Dasar I Per.09
- 18. Nuclear Energy The sun’s energy is produced from a nuclear fusion reaction in which hydrogen nuclei fuse to form helium nuclei. 07/03/11 © 2010 Universitas Negeri Jakarta | www.unj.ac.id |
- 26. Chemical Heat Mechanical 07/03/11 © 2010 Universitas Negeri Jakarta | www.unj.ac.id |
- 30. Work Done by a Constant Force (II) Work and Energy Example: Work done on the bag by the person.. Special case: W = 0 J a) W P = F P d cos ( 90 o ) b) W g = m g d cos ( 90 o ) Nothing to do with the motion 07/03/11 © 2010 Universitas Negeri Jakarta | www.unj.ac.id |
- 36. Example 2 (cont’d) Work and Energy (1) W net = F d (a) cos 180 o = - F d (a) = 0 – m v (a) 2 / 2 - F x (20.0 m) = - m (16.7 m/s) 2 / 2 (2) W net = F d (b) cos 180 o = - F d (b) = 0 – m v (b) 2 / 2 - F x ( ? m) = - m (33.3 m/s) 2 / 2 (3) F & m are common. Thus, ? = 80.0 m 07/03/11 © 2010 Universitas Negeri Jakarta | www.unj.ac.id |
- 37. Work-Energy Theorem Work and Energy W net = F net d = ( m a ) d = m [ ( v 2 2 – v 1 2 ) / 2d ] d = (1/2) m v 2 2 – (1/2) m v 1 2 = K 2 – K 1 07/03/11 © 2010 Universitas Negeri Jakarta | www.unj.ac.id |
- 38. Spring Force (Hooke’s Law) Work and Energy F S (x) = - k x F P F S Natural Length x > 0 x < 0 Spring Force (Restoring Force): The spring exerts its force in the direction opposite the displacement. 07/03/11 © 2010 Universitas Negeri Jakarta | www.unj.ac.id |
- 39. Work Done to Stretch a Spring Work and Energy x 2 W = F P (x) dx x 1 F S (x) = - k x W Natural Length F P F S 07/03/11 © 2010 Universitas Negeri Jakarta | www.unj.ac.id |
- 40. Work Done by a Varying Force Work and Energy l b W = F || dl l a l 0 07/03/11 © 2010 Universitas Negeri Jakarta | www.unj.ac.id |
- 44. Example 2 (cont’d) Work and Energy (a) The work done by the spring is (b) W f = - k F N ( x 2 – x 1 ) = -4.41 (0 + 0.200) (c) W net = W S + W f = 5.00 - 4.41 x 0.200 (d) Work-Energy Theorem : W net = K 2 – K 1 4.12 = (1/2) m v 2 – 0 v = 2.34 m/s x 2 = 0 m W S = F S (x) d x = +5.00 J x 1 = -0.200 m 07/03/11 © 2010 Universitas Negeri Jakarta | www.unj.ac.id |
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