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Forces Flashcards

(56 cards)

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1
Q

a vector has…
a scalar has…

A

magnitude and direction
just magnitude

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2
Q

… cannot be negative but… can

A

scalars
vectors

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3
Q

examples of scalar

A

speed
distance
time
mass
energy

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4
Q

examples of vector

A

velocity
displacement
acceleration
force
momentum

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5
Q

what is scalar

A

can be measured with a number (magnitude)

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6
Q

what is a vector quantity

A
  • measured with a number
  • BUT ALSO
  • has a direction
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7
Q

gravity- the larger the… the stronger the… the greater the…

A

mass
field
attraction

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8
Q

weight calculation

A

weight = mass x gravitational field strength

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9
Q

weight is measured using a… by…

A

force meter / calibrated spring-balance
by the weighing scales measuring the force you exert then divides by 10 to get the mass

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10
Q

gravitational field strength on earth

A

9.8

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11
Q

what happens to mass and weight of the same person on two different planets

A

mass stays the same
wieght is different because gravitational field strength is different

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12
Q

skydiver example of resultant forces

A
  1. initially, there is no air reisstance so only force acting on him is weight = accelerates
  2. air resistance increases, resultant force from weight decreases= acceleration decreases
  3. eventually equal and balance, so no resultant force = no acceleration
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13
Q

work done =

A

work done = force x distance

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14
Q

one joule of work is done when…

A

a force of one newton causes a displacement of one metre
1 joule = 1 newton metre

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15
Q

to stretch, bend of compress an object… need to be applied otherwise…

A

multiple forces need to be applied otherwise it will just move in one direction

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16
Q

elastic deformation

A

the object returns to its original shape when the load has been removed

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17
Q

plastic deformation

A

the object does not reutrn to its original shape when the load has been removed, this can be a spring when pulled too far

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18
Q

Hooke’s law

A

the extension of an elastic object, is directly proportional to the force applied, provided that the limit of proportionality is not exceeded

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19
Q

hooke’s law calculation

A

F = kx
Force = spring constant x extension
N Nm-1 m

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20
Q

hooke’s law : why does the graph stop being linear

A
  • the limit of proportionality has been reached, no longer obeys hooke’s law
  • turns to plastic behaviour (object pulled too far)
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21
Q

hooke’s law: if the graph is just linear with no non-linear end seciton…

A

… the material is brittle, so snaps instead of stretching afte tthe elastic limit

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22
Q

work done (spring) calc

A

work done = 1/2 x spring constant x extension squared

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23
Q

the work done on the spring =

Study These Flashcards
A

= the elastic potential energy stored

24
Q

moment of a force =

Study These Flashcards
A

moment of a force = force x perpendicular distance
M = Fd

25
(roations and moments)equilibrium is when...
sum of anticlockwise moments = sum of clockwise moments
26
Gears: if a gear (1) is connected to another gear (2)with fewer teeth (smaller)
- second gear with turn faster - but with less force - in opposite direction to first gear
27
if a gear (1) is connected to a gear (2) with more teeth (larger)
- turns slower - more force - in opposite direction
28
pressure calc
pressure = force / area
29
pressure in fluids: an object floats if its weight is...
less than the weight of the water it displaces
30
buoyancy is the...
upwards force that counteracts the weight of the floating object
31
objects that float have a lower...
density than the water so the weight of the equivalent amount of water is greater than the weight of the floating object
32
pressure due to a column of liquuid =
pressure due to a column of liquid = height of column x density of liquid x gravitational field strength p = hpg
33
upthrust (liquid)
- a partially or totally submerged object experiences a greater pressure on the bottom surfacr than the top surface - this creates a resultant force upwards (upthrust)
34
earth's atmosphere
thin layer on air around the earth which gets less dense with increasing altitude
35
explain why there the atmosphere gets less dense with increasing altitude
- the weight of the air is the force which causes the pressure - so higher up, there are fewer air molecules than lower down - so smaller weight so less pressure
36
assumptions made for a simple modle of the atmosphere
- isothermal (all at the same temp) - transparent to solar radiation - opaque to terrestrial radiation
37
if an object is moving in a circular motion, the acceleration... because...
increases because changing velocity is defines as acceleration so the change in direction means it accelerates
38
speed equation
speed = distance/ time
39
displacement time graphs: - sharper gadient means... - negative gradient means... - horizontal line means... - curved line means...
sharper gradient = faster speed negative gradient = returning back to starting point horizontal line = stationary curved line = velocity is changing
40
velocity-time graphs: gradient is... sharper gradient means... negative gradient means... horizontal line means... 0 velocity means... curved line means...
gradient is acceleration sharper gradient is greater acceleration negative gradient is deceleration horizontal line is constant speed 0 velocity is stationary curved line means acceleration is changing
41
falling in a fluid
1. initially object will fall under gravity 2. but then the drag forces will act and the object will move at terminal velocity
42
Netwtons first law
an object has a constant velocity unless acted on by a resultant force
43
Newton's second law
the acceleration of an object is proportional to the resultant force acting on the object, and inversely proportional to the mass of the object.
44
equation linking force, acceleration and mass
force = mass x acceleration
45
inertia
the measure of how difficult it is to change the velocity of an object
46
inertial mass =
inertial mass = force/ acceleration
47
newton's third law
whenever two objects interact, the forces they exert on each other are equal and opposite
48
vehicle stopping distances
1. after seeing a hazard, there is reaction time during which you travel x metres (thinking distance) 2. then you react, causing the car to slow down and stop over y metres (braking distance)
49
to find reaction time... (practical)
ruler drop test
50
when a force is applied to the brakes of a vehicle...
1. energy is transferred (by friction) to the wheel 2. so the vehicle's kinetic energy decreases 3. and temp on the brakes increase
51
momentum =
momentum = mass x velocity p = mv
52
momentum is always conserved in a...
collision or explosion (where there ar eno external forces like air resistance etc)
53
equation linking force, time and change in momentum
force = change in momentum / time
54
Safety features in cars - seatbelts
1. seatbelts - stretch under large forces, stretching increases distance move slightly but extends the time taken for passengers to stop, decreases rate of change of momentum and therefore reduces force
55
safety features in cars - crumple zones
- without them cards would be a solid metal block which stops immediately - softer areas at the front of the car which crumple upon a crash - absorbs energy to deform and compact - increases time taken for car to stop therefore reduced acceleration and force on passengers
56
safety features in cars - air bags
- without these your head would whip forward hitting the steering wheel - inflates insantly upon a crash - your head hitd this and slows down - increases time taken for head to stop moving so reduces force on neck

Physics (10 decks)

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