P5 Forces and Density Flashcards

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1
Q

how do you calculate mass?

A

volume x density
or
weight / gravity

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2
Q

how do you measure the volume of an irregular object?

A

displacement of water

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3
Q

how do you calculate density?

A

mass/volume

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4
Q

how do you calculate volume?

A

mass/density

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5
Q

what is the tool used to measure very small distances?

A

micrometer screw gauge

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6
Q

what is force?

A

a PUSH/PULL that can change the SIZE, SHAPE and MOTION of a body

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7
Q

what is force measured in?

A

Newtons (N)

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8
Q

how do we draw force diagrams?

A

ARROW shows direction

LABEL (…N) shows magnitude

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9
Q

what is a resultant force?

A

the net force acting on an object

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10
Q

what happens when forces are balanced?

A
  • no resultant force

- object at rest or constant speed in straight line

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11
Q

what happens when forces are unbalanced?

A
  • there’s a resultant force

- the object accelerating or decelerating

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12
Q

F = ?

A

ma (newton’s 2nd law)

kx (hooke’s law)

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13
Q

what does F=ma tell us?

A
  • force directly proportional to acceleration

- mass inversely proportional to acceleration

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14
Q

what is friction?

A

force that opposes motion + produces heat

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15
Q

what is air resistance?

A

friction due to movement through air.

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16
Q

what is the difference between mass and weight?

A

M: the amount of matter, kg, doesn’t change
W: force of gravitational field strength on mass, N, changes w gravity

17
Q

how do you calculate weight?

A

mass x gravity

18
Q

unit for mass

A

kg

19
Q

how do you calculate gravity?

A

weight / mass

20
Q

what is hooke’s law?

A

force is directly proportional to extension (F = kx)

21
Q

what are k and x in F=kx?

A

k is spring constant

x is extension

22
Q

what is the limit of proportionality?

A
  • the point at which Hooke’s Law no longer applies

- graph no longer linear

23
Q

what happens if we keep adding more load to a spring?

A
  1. reaches limit of proportionality and hooke’s law no longer applies
  2. breaks
24
Q

what is the centre of mass?

A

where the mass of an object is concentrated

25
Q

how do you determine an irregular object’s centre of mass?

A
  1. hang lamina from a point
  2. mark vertical line
  3. hang lamina from second point
  4. mark second vertical line
    → centre of mass is there the lines intersect
26
Q

how does weight act on an object?

A

from centre of mass

vertically downwards

27
Q

when does an object fall?

A

when the centre of mass falls beyond either side of the base

28
Q

what is MOMENT?

A

TURNING EFFECT away from centre of mass

29
Q

when would you say a system is in equilibrium?

A

no resultant force

no turning effect

30
Q

how do you calculate moment?

A

distance from pivot x perpendicular force

31
Q

define gravitational field + example

A

where mass experiences force

e.g. earth

32
Q

what is upthrust?

A

the upward force that a liquid or gas exerts on a body

33
Q

what does a directly proportional graph look like?

A
  • straight line

- through the origin