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Principles of Physics. Objects have energy if they are able to do things  A way of explaining why things happen  Energy is a scalar quantity (no direction)

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Presentation on theme: "Principles of Physics. Objects have energy if they are able to do things  A way of explaining why things happen  Energy is a scalar quantity (no direction)"— Presentation transcript:

1 Principles of Physics

2 Objects have energy if they are able to do things  A way of explaining why things happen  Energy is a scalar quantity (no direction)

3

4 Energy of Motion KE = ½ mv 2 KE = Kinetic energy (Joules = J) m = mass (kg) v = velocity (m/s)

5 A 5 kg block is sliding on a frictionless horizontal surface with a speed of 5 m/s. Calculate the kinetic energy of the block KE = ½ mv 2 = ½ (5)(5) 2 KE = 62.5 J

6 Energy of position or condition Gravitational PE= mgh PE = potential energy (J) m = mass (kg) g = gravitational acceleration = 9.8 m/s 2 h = height (m) Other types of PE: spring, electrostatic

7 A 0.100kg egg is dropped from the top of the bleachers which are 5.5 m high. Calculate the potential energy of the egg. PE = mgh PE = (0.100)(9.8)(5.5) PE = 5.39 J

8 Total mechanical energy of a system: All the potential energy and all of the kinetic energy that the system contains

9 A toy airplane with a mass of 30 kg is travelling 35 m above the ground at 40 m/s. How much mechanical energy does the airplane have? KE = ½ mv 2 PE = mgh KE = ½ (30)(40) 2 PE = (30)(9.8)(35) KE = 24,000 JPE = 10,290 J Total Mechanical Energy = 24,000+10,290 = 34,290 J


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