Pressure Flashcards

1
Q

What is pressure?

A

The force exerted perpendicularly per unit area

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2
Q

Formula for pressure

A

Force/Area

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3
Q

What are the units for pressure?

A

N/m2 or Pa (Pascal) or cmHg (for pressure in air)

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4
Q

Why does a nail have a pointed end?

A

A small force will be required to drive the nail into a wall

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5
Q

Formula for pressure in liquids

A

Depth of object x density of liquid x gravity (10m/s2)

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6
Q

What does the pressure in liquids depend on?

A

Density and depth of object

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7
Q

What is atmospheric pressure?

A

It is the pressure exerted by air molecules on the Earth surface

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8
Q

What is the value of atmospheric pressure?

A

103000Pa or 76cmHg

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9
Q

Why does air pressure decrease with altitude?

A

Because there are less air molecules

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10
Q

Why does our nose bleed sometimes when we climb a moutain?

A

At the top, air pressure is less than pressure inside our body and therefore blood moves from high pressure to low pressure

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11
Q

What is used to measure air pressure?

A

A mercury barometer

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12
Q

What is a mercury manometer used for?

A

It is used to measure pressure of a gas in a cylinder or air in a tyre

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13
Q

What formula applies to gas when the temperature constant?

A

P1V1 = P2V2

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14
Q

Why shouldn’t a hot air balloon be fully inflated before taking off?

A

When the balloon moves up, air pressure will decrease and the volume of the balloon will increase because the pressure inside will be relatively greater.
If the hot air balloon is fully inflated before take off, the balloon will burst when it is up in the air

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