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Work, Energy and Power. Is the student doing work in pushing against the wall?

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Presentation on theme: "Work, Energy and Power. Is the student doing work in pushing against the wall?"— Presentation transcript:

1 Work, Energy and Power

2 Is the student doing work in pushing against the wall?

3 Is the girl doing work in pushing the cart?

4 Is the man doing work in carrying the load across the street?

5 Is the lady doing work while holding the weights above her head?

6 Is work done in lifting the box?

7 Is work done in putting down the box?

8 Work If a constant force F acts on an object as it undergoes a displacement d, the work done by the force on the object during the displacement is W = Fdcos where W = work done in Joules (J) F = force in N d = displacement in m = angle (180 or less) between the direction of F and the direction of d Note: 1 J = 1 Nm

9 Work

10 Requirements in order for work to be done 1. Force need to be exerted 2. There must be a displacement 3. The force must be exerted in such a way that it has a component that is in the same direction or opposite to the direction of the displacement.

11 Energy The capacity of a physical system to do work.

12 Kinetic Energy (KE)

13 Gravitational Potential Energy (PE g )

14 Elastic Potential Energy (PE s )

15 Work-Energy Calculation When a system gains or loses energy from its environment because of work done on the system by forces origination in the environment, then the change in the systems energy is W = E f – E i Rearranging and substituting for the different types of energy results to KE i + PE gi + PE si + W = KE f + PE gf + PE sf

16 Law of conservation of energy In a closed, isolated system, energy is not created or destroyed, but rather, is conserved. KE i + PE gi + PE si = KE f + PE gf + Pe sf

17 Power


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