# Physics Flashcards

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• Created by: Sophie
• Created on: 08-05-14 23:22
Brownian Motion
The continual random movement of microscopic particles. When particles collide into one another, this causes a change in speed and direction of the particles, making them randomly move about.
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How does a gas exert a pressure on the walls of its container?
Billions of tiny air particles move about in continual random motion. Particle collisions with the walls of the container exerts a force, which gets distributed over the area of the wall of the container, hence, exerting a pressure.
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Converting Kelvins to Celsius
-273
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Converting Celsius to Kelvins
+273
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Pressure Law
With a fixed mass of gas at a constant volume, pressure is proportional to temperature (in Kelvins).
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Boyle's Law
At a constant temperature and with a fixed mass of gas, pressure is inversely proportional to volume.
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KE Law
The temperature of a gas (in Kelvins) is proportional to the average kinetic energy of its particles
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Principle of the conservation of energy
Energy can never be created or destroyed, only transferred from one form to another
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Loft Insulation
A thick layer of fibreglass is placed on the loft floor, reducing the heat lost through conduction into the roof space from the ceiling
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Hot Water Tank Jacket
Lagging such as fibreglass wool reduces conduction and radiation
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Double Glazing
Two layers of glass with a narrow air gap inbetween, reducing conduction and convection
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Thick Curtains
Big pieces of cloth over windows that reduce radiation and conduction
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Cavity Wall Insulation
Foam squirted into the gap between bricks stops convection currents being set up in the gap, and radiation across the gap. Insulating foam and air pockets trapped in it, reduce heat loss by conduction.
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Draught Proofing
Strips of foam/plastic around windows/doors prevent draughts of cold air blowing in, reducing convection.
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Humans-Clothes
Reduces heat transfer. Pockets of air trapped between layers reduces conduction and convection (air is an insulator). Also reduces radiation as material absorbs some heat radiated from our bodies.
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Humans-Hairs
Hairs stand up, trapping a thick layer of insulating air around the body. Reduces convection.
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Animals-Feathers
Fluff them up to trap air.
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Animals-Curl up
Reduces exposed surface area
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Why are marathon runners wrapped in foil blankets?
They prevent the loss/gain of body heat by reflecting the heat radiation away through its shiny surface. They want to prevent the runner having a sudden drop in body temperature.
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What is velocity?
Speed in a particular direction
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Distance-time Graph: What does a horizontal line represent?
The object is stationary
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Distance-time Graph: What does a sloped straight line represent?
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Distance-time Graph: What does an increasing gradient represent?
Acceleration
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Distance-time Graph: What does an decreasing gradient represent?
Deceleration
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Velocity-time Graph: Horizontal line
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Velocity-time Graph: Uphill
Acceleration
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Velocity-time Graph: Downhill
Deceleration
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Velocity-time Graph: Curve
Changing acceleration
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Speed
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Acceleration
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What happens when a skydiver jumps out a plane?
Accelerate until reaches terminal velocity. Parachute opens, it'll cause sudden drag force increase. Unbalanced force acting upwards, causing her to decelerate. Drag force decreases and new terminal velocity reached.
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Newton's 1st Law of Motion
If the forces on an object is balanced – there is no resultant force – the object will either remain at rest or carry on moving at constant speed in a straight line.
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Newton's 2nd Law of Motion
If the forces on an object is unbalanced, the object will accelerate.
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Newton's 3rd Law of Motion
For every action there is an equal and opposite reaction.
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Explain terminal velocity 1
At the start, the object accelerates downwards because of its weight. There is no air resistance. There is a resultant force acting downwards.
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Terminal velocity 2
As it gains speed, the object's weight stays the same, but the air resistance on it increases. There is a resultant force acting downwards.
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Terminal velocity 3
Eventually, the object's weight is balanced by the air resistance. There is no resultant force and the object reaches a steady speed, called the terminal velocity.
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Electricity-Double Insulation
Most modern appliances are made from an insulator like plastic. Electrical parts are covered with plastic so if a fault develops, the dangerous parts won’t be touched by the user. Double insulation doesn’t require an earth wire.
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Electricity-Earthing
Appliances with metal casing should be connected to earth wire so if live wire is frayed and comes into contact with casing, earth wire provides low resistance path for current for electricity to pass down to earth without giving user electric shock
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## Other cards in this set

### Card 2

#### Front

Billions of tiny air particles move about in continual random motion. Particle collisions with the walls of the container exerts a force, which gets distributed over the area of the wall of the container, hence, exerting a pressure.

#### Back

How does a gas exert a pressure on the walls of its container?

-273

+273

### Card 5

#### Front

With a fixed mass of gas at a constant volume, pressure is proportional to temperature (in Kelvins).