# Physics

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## Energy Transfer!

1) Electrical energy --> whenever a current flows

2) Light energy --> from the Sun, light bulbs.

3) Sound energy --> from loudspeakers to anything noisy

4) Kinetic energy --> anything that moves

5) Nuclear --> released only from nuclear reactions

6) Thermal energy --> flows from hot objects

7) Gravitational potential energy --> possessed by anything that can fall

8) Elastic potential energy --> possessed by springs, elastic

9) Chemical energy --> possessed by foods, fuels, batteries

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## Energy Conversations

ENERGY CONSERVATION: This is about using fewer resources because of the damage it is doing to the world and they might run out one day.

THE PRINCIPLE OF THE CONSERVATION OF ENERGY: It's an all-pervading principle which governs the working of entrie physical universe. It is stated as:

"ENERGY CAN NEVER BE CREATED NOR DESTROYED. IT'S ONLY CONVERTED FROM ONE FORM TO ANOTHER."

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## Efficiency

Efficiency = USEFUL ENERGY OUTPUT / TOTAL ENERGY INPUT

EXAMPLE:

"An ordinary lightbulb is 5% efficient. If 1000 J of light energy is given out, how much is energy wasted?"

1000 J / 0.05 = 20,000 J

20,000 - 1000 = 19,000 J

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## Gravitational Potential Energy

GPE = mass x gravitational field strength x height

m x g (10) x h

EXAMPLE:

"On Earth, a ball of mass 0.5kg is kicked straight up. How much GPE does it have at its highest point 6m off the ground?"

0.5 x 10 x 6 = 30 J

Moon = 1.6N/ kg

Jupiter = 26N/ kg

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## Kinetic Energy

KE = 1/2 mv²

OR

KE = 1/2 x m x v²

KE = Joules

M = Kilograms

V = m/s

EXAMPLE:

What is the kinetic energy of a 1000 kg car travelling at 5 m/s?

1/2 x 1000 x 25 = 12,500J --> The 5 is squared, therefore it is 25.

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