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ENERGY = THE ABILITY TO DO WORK
WORK = ENERGY TRANSFERRED

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Principle of Conservation of Mechanical Energy = The total mechanical energy (sum of gravitational potential energy and kinetic energy) in an isolated system remains constant. 

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Principle of Conservation of Mechanical Energy = The total mechanical energy (sum of gravitational potential energy and kinetic energy) in an isolated system remains constant. 

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Product of force parallel to movement and the displacement of a body

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When is W positive?

When is W negative?

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Physics, Positive Work vs. Negative Work for Horizontal Motion

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Work done by forces in different directions

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Work done by forces in different directions

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Work example problems | Work and energy | Physics | Khan Academy

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Is work done on a tray that is carried by a waiter moving at constant speed?

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Is work done on a tray that is carried by a waiter moving at constant speed?

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NO.
The force applied on the tray is vertically upwards to overcome the force of gravity on the tray, and there is no part (component) of that force that acts in the same direction as the displacement horizontally.

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Physics - Mechanics: Work, Energy, and Power (10 of 20) Work Done by Carrying a Box

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Principle of Conservation of Mechanical Energy states:
In the absence of external forces, the total mechanical energy in a system is CONSTANT.

Def for mechanical energy:
Mechanical energy is the sum of gravitational potential energy and kinetic energy at a point.

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Answers p. 13-16

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Work-Energy Theorem = The work done on an object by a net force is equal to the change in the object's kinetic energy

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Work-Energy Theorem = The work done on an object by a net force is equal to the change in the object's kinetic energy

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W net = ΔE k

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Physics, Work Energy Theorem, An Explanation

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Wnc  = ∆E k + ∆E p

Example:
A sphere of mass 2 kg is shot vertically upwards from ground level and reaches a maximum height of 4 m above the ground. A constant frictional force of 5,4 N acts on the sphere throughout its motion.
Calculate the initial velocity of the sphere.

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Conservative and Non Conservative Forces

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Wnc  = ∆E k + ∆E p

W nc = F f ∆xcosθ = F f ∆x cos180 = 5.4 x 4 x (-1) = -21.6 J

∆E p =  mgh f - mgh i = 2*9.8*4 – 0 = 78.4 J

∆E k = ½ mv f ² -½ mv i ²    = 0 – ½ x 2 x v i ² = - v i ²

Wnc  = ∆E k + ∆E p

.: -21.6 = - v i ² + 78.4         .: v i = √(21.6 + 78.4) = 10 m.s⁻¹

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Work done by forces acting on inclined plane

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Work done by forces acting on inclined plane

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Physics - Mechanics: Work, Energy, and Power (7 of 20) Inclined Plane (Friction)

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Physics - Mechanics: Work, Energy, and Power Examples (27 of 27) % Work Lost Due to Friction

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Answers p.19-43 NOTES

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Power | Work and energy | Physics | Khan Academy

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📚 How to solve any percent efficiency problem

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Answers Power

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Conservative & Nonconservative Forces, Kinetic & Potential Energy, Mechanical Energy Conservation