Applied science level 3 btec > unit 5 physics work done > Flashcards

unit 5 physics work done Flashcards

(49 cards)

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1
Q

What is the ability of energy?

A

To do work.

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2
Q

What is work?

A

Work is done when the point of applciation of a force moves.

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3
Q

What happens when work is done.

A

Energy is transferred like heat for example.

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4
Q

What unit is work measured?

A

It is measured in joules.

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5
Q

What is the equation for work done?

A

Work done=force times distance.

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6
Q

What is the equation for heat ?

A

Heat (joules)=change in internal energy (joules) plus work done (joules).

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7
Q

What is power?

A

Power is the rate at which work is done, I.e the amount of work done every second.

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8
Q

Unit for power?

A

Power is measured in watts.

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9
Q

What does the system plus surroudnigns make?

A

The system plus the surroundings make the unvierse.

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10
Q

What is a system in physics term?

A

The part of the universe whose properties you are investiagting. It is enclosed by a boundary defined by you, the experimenter.

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11
Q

What is the meaning of surroundings?

A

the rest of the universe, outside of the boundary.

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12
Q

What happens when work is done on an object?

A

Energy is transferred or moved to it.

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13
Q

What is thermal energy?

A

The total kinetic energy of all the particles making up that object.

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14
Q

What is definition of heat?

A

Heat is the movement of thermal energy between two objects at different temperatures.

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15
Q

What happens as heat is added into a system?

A

As heat is added into a system, the particles absorb the themal energy which increases the kinetic energy of the particles and the potential energy which is stored in the chemical bonds energy.

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15
Q

What is meaning of the internal energy?

A

Internal energy is the sum of kinetic and potential energies of the particles making up the system.

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15
Q

What is the equation for first law of thermodynamics for heat added?

A

Heat added which is measured in joules=change in internal energy+work done by the system.

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15
Q

For the first law of thermodynamics equation if heat is added to the system what is Q?

A

Q is positive.

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15
Q

What is Q when heat is taken out of the system?

A

Q is negative.

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15
Q

How to calcualte work done?

Study These Flashcards
A

Work done=force times distance moved in the direction of the force.

15
Q

How does heat and expansion of gases work?

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A

When heat is added, the pressure of the gas increases, providing a force greater than the weight of the piston, causing the piston to move up. The increase in volume of the gas will decrease the pressure until it returns to the initial pressure that balanced the weight of the piston.

15
Q

What are the four gas laws to remember?

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A

Charles law-The volume of an ideal gas is directly proportinal to its kelvin temperature if the pressure and amount of gas are fixed. Boyles law-The pressure of an ideal gas is inversely proportinal to its volume if the kelvin temperature and amount of gas are fixed.

15
Q

What is Avogadros law?

Study These Flashcards
A

The volume of an ideal gas is directly proportinal to its amount (number of moles). if temeprature and amount of gas are fixed.

15
Q

What is gay Lusaacs law?

Study These Flashcards
A

The pressure of an ideal gas is directly proportinal to its kelvin temperature if the volume and amount of gas are fixed.

15
What is the ideal gas equation?
PV=NKT or PV=NRT. P=pressure Volume=volume of gas in cubic metres. N=number of particles, K=Boltzmans constant, T=temperature in kelvin, N=number of moles and R=gas constant.
15
What is the isothermal process?
Constant temperature and the temperature of the gas does not change. This is because the gas expands or compresses slowly, heat can flow in or out of the gas, heat transfer balances the work done and the internal energy stays constant. The gas expands or compresses slowly. Heat can flow in or out of gas, heat transfer balances the work done and internal energy stays constant.
15
what does adiabatic processes do?
Expansion or compression happens quickly, gas is insulated, temperature changes, and work done changes internal energy. Expansion or compression happens quickly, gas is insulated, temperature changes and work done changes the internal energy. Heat is not added and if gas is compressed internal energy will increase and if gas is expanded internal energy will decrease.
16
What is stage one of carnot cycle?
stage one:isothermal expansion:gas in contact with hot reservoir. 2. temperature stays constant,gas expands, heat flows into gas and gas does work.
17
Stage 2 of carnot cycle?
Adiabatic expansion:Gas is insulated, no heat transfer, gas continues to expand and so temperature falls.
18
Stage three of carnot cycle?
Isothermal compression:Gas in contact with cold reservoir, temperature stays constant, gas is compressed and heat flows out of the gas.
19
Stage 4 of carnot cycle?
Adiabatic compression:Gas insulated again, no heat transfer, gas is compressed and temperature rises back to original value.
20
Meaning of reversible processes?
The system can return to its original state, surroundings remain unchanged and the process follows the same path on a pressure-volume diagram.
21
What is intermediate steps?
The gas passing through many tiny stages, each stage has a slightly different pressure and volume and these stages are called intermediate states.
22
What is infinitesimal steps?
Extremely small changes,almost zero differences each time and importance of this is that the system stays in equilibrium, pressure and temperature stays the same and the process can be reversed exactly.
23
What is irrervsible processes?
Cannot return both system and surroundings to their original states. Always leaves permanent change in environment and happens naturally.
24
What is entropy?
A measure of disorder or randomness of particles.
25
What happens in one carnot cycle?
Heat enters the system from a hot reservoir, some heat is turned into useful work, the rest of the heat leaves the system to the cold reservoir (Qout), Qin is always greater than Qout.
26
Why can heat not fully turn into work?
Work can fully turn into heat but some heat can not turn into work as it lost to the surroundings.
27
Why are real engines not efficient?
Have friction, lose heat to surrondings, are not reversible and operate quickly.
28
Why are carnot engines ideal?
Operate slowly, have no energy loss, use reversible processes and are extrememly slow.
29
How do heat engines actually work?
take in heat from a hot source, converts some to work, dump remaining heat to a cold sink and repeat process in a cycle and example are petrol engine,diesel engine, steam tubine and gas turbine.
30
Why is carnot efficiency the maximum?
Depends on only TH and TC, no real engine can exceed it and inceeasing TH or decreasing TC increases efficiency.
31
What is the otto cycle?
Ideal cycle for a petrol engine and shows stages of intake, compression,ignition and exhaust.
32
What is step one for otto cycle?
Intake-where the piston movs down, drawing air fuel mixture into cyclinder,inlet valve opens and volume increases, prssure stays constant.
33
Step 2 of otto cycle?
Compression-piston moves up, compression mixture. inlet valve closes, no heat transfer-adiabatic compression and PV diagram:curve sloping upwards.
34
What is step 3 of otto cycle?
ignition:spark ignites the mixture-pressure rises. Piston is stationary, volume constant-vertical line. Heat energy increases-temperature rises.
35
Step 4 of otto cycle?
High pressure gas pushes piston down. Work is done on piston-mechanicla energy and no heat transfer-adiabatic expansion.
36
Stage 5 of otto cycle?
outlet valve stays open-some exhaust gas escapes. Piston stationary-volume constant, pressure drops.
37
Stage 6 of otto cycle?
Exhaust stroke-Piston moves up,expelling remaining gases. Volume decreases, pressure constant.
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