Physics - Chapter 7 - Energy

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Grade 9 Physics - Energy (Cambridge GSCE O-level Core Standard)

22 Terms

1

Energy

The ability to do work.

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2

Is energy a vector or a scalar quantity?

Scalar quantity, as direction isn’t important.

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3

Work done

The force applied multiplied by the distance travelled in the direction of the force.

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4

Formula of Work done

W.D = F x s

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5

Power

The rate at which energy is used. (How much energy is used per second)

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6

Formula of Power

P = E/t

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7

Potential Energy (Stored Energy)

The energy a body has because of its position or condition.

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8

The three different types of potential energies are…

Chemical P.E, Elastic P.E, Gravitational P.E

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9

Gravitational Potential Energy

Found in all objects which are at some height above the ground.

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10

Formula of Gravitational P.E

Gravitational P.E = m x g x h

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11

Kinetic Energy

The energy a body has for its motion.

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12

Formula of Kinetic Energy

KE = mv² / 2 or ½ x mv²

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13

Principle of Conservation of Energy

Energy is neither created nor destroyed, but is always conserved (Changing from one form to another.).

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14

Formula for efficiency (of electrical appliances)

Useful Energy Output/Total Energy Input x 100

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15

What happens when an object falls from a height above the ground?

Gravitational P.E → Kinetic Energy → Sound Energy, Heat Energy, and W.D to break the object and/or the ground

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16

Formula of efficiency (Of a ramp)

W.D against gravity/W.D by person x 100

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17

What are the types of energies which are wasted when using a ramp?

  • Sound energy

  • W.D against Friction: Wasted due to friction between the object and the ramp surface.

  • Heat energy

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18

What if a ramp has no friction?

This means that there are no energy losses. Therefore W.D by person = W.D against Gravity (Efficiency = 100%)

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19

Energy transfer in a boiler (Power Station)

Chemical Potential Energy → Heat Energy

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20

Energy transfer in a turbine (Power Station)

Heat Energy → Kinetic Energy

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21

Energy transfer in a generator (Power Station)

Kinetic Energy → Electrical Energy

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22

Wasted energy in a power station

Heat Energy and Sound Energy

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