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Science 10 AP: Physics > Energy > Flashcards

Energy Flashcards

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1
Q

What is energy?

A

Greek for “active”
An object’s ability to do work (work is the transfer of energy)

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2
Q

What is gravitational potential energy?

A

The energy that things will have due to it’s position (usually height) relative to the surface of the Earth, or another object. It is released by falling. E(p) = mgh or F(g) (weight) x h

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3
Q

What is gravity and 9.81 m/s^2?

A

Gravity is a property of all objects with mass that causes them to accelerate towards each other.
g is the rate of acceleration that falling objects experience because of Earth’s mass

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4
Q

What is potential chemical energy?

A

The energy that is stored inside the chemical bonds of compounds?
Exothermic: gives off heat (energy)
Endothermic: takes in heat (energy)

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5
Q

What is potential electrical energy?

A

Work done by moving electrical charges

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6
Q

What is potential nuclear energy?

A

Energy is stored in the nucleus of an atom. E = ∆mc^2

Nuclear fission: atom is split ex: bomb, power plant
Nuclear fusion: atoms combine ex: Sun

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7
Q

Explain the chain reaction in nuclear power.

A

A neutron hits a big atom’s nucleus, then splits into 2 new atoms. It loses some neutrons, that further split more nuclei.

Mass from the nucleus is converted into energy. Products do not add up to the mass you start with.

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8
Q

What is potential solar energy?

A

Solar energy results from a nuclear fusion reaction (the Sun) and travels to Earth as electromagnetic radiation.

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9
Q

What does it mean for an object to be elastic?

A

Returns to its original shape after being distorted. ex: spring, elastic band.

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10
Q

What is elastic potential energy?

A

Work is done on an elastic object to distort it. The stored energy gets released when the deformed object returns to its original shape.

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11
Q

What is (potential) thermal energy?

A

Moving particles. (heat) (wasted energy)

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12
Q

What is kinetic energy?

A

“actively moving”, meaning motion. Measured easily. E(k) = 1/2mv^2

IS NOT A VECTOR. ANY MOTION COUNTS. PARTICLES MOVING, HEAT/TEMP?

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13
Q

What is potential energy?

A

stored energy, “held in readiness”. Can do work or cause motion but not moving yet.

ALSO ∆E(p) = W

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14
Q

What is mass?

A

Quantity of matter in an object. It doesn’t change under different conditions. In kg. F = ma (Newtons’ 2nd law)

Scalar

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15
Q

What is weight?

A

The force of gravity acting on a mass. It changes if gravity changes. In Newtons. F(g) = mg (g is gravity acceleration)

Vector

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16
Q

What is Mechanical Energy?

A

The total (Ep and Ek) energy in a system (the thing I’m looking at right now).

An object can have both kinetic and potential the same time (planes and birds).

Em = Ep + Ek (= Etotal)

17
Q

What happens to the energy of an object when it falls off a cliff?

A

Since an object has only potential energy when it is not moving at the top of a height, and only kinetic energy when it no longer has height, but only speed…

Ep (top) = Ek (bottom)

Falling, then throwing up. Neglecting air resistance.

18
Q

What is an energy conversion or transformation?

A

Any time energy is turned from one form to another.

Evidence is production or light, or motion, or change in shape, or change in temperature.

In all energy transformations heat is a by-product as a result of friction.

19
Q

What is useful energy?

A

(Output) Energy used to perform the desired task. For example, work.

20
Q

What is wasted energy?

A

(Output) Energy that does not do anything “useful”. Most common is heat, also sound.

Can be useful in for example cooking.

21
Q

What is energy efficiency?

A

The ratio of the work or energy produced by a machine, to the work (energy) put into that machine.

E = useful output/input (x100%) IDENTIFY WHAT’S INPUT AND OUTPUT

Total Energy Input = Useful Energy Output + Other Energy OutputWh

22
Q

What energy transformations are happening in a coal burning generator (#1 in CA)?

A

Chemical > Thermal > Thermal (water) > Steam Pressure (Work) -> Mechanical Kinetic > Electrical

30% efficient, lots of steps

23
Q

What energy transformations are happening in a nuclear reactor (#2 in CA)?

A

Nuclear > Thermal (coolant) > Thermal (water) > Steam > Mechanical Kinetic > Electrical (no CO2, though)

30% efficient, similar to coal, lots of steps, but just without CO2 and chemical energy

24
Q

What energy transformations are happening in a hydroelectric generator (#3 in CA)?

A

Gravitational potential > kinetic energy (water) > Mechanical Kinetic > Electrical

(No CO2) (70-90% Eff)

Less steps, as production of heat often leads to the loss of energy.

25
Q

Is energy a scalar or a vector?

A

Scalar

Science 10 AP: Physics (3 decks)

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