Force And Pressure 8 IJSO Flashcards
Instrument used to measure the atmospheric pressure
Barometer
SI unit of force
Newton
Pressure formula
Force/ area
SI unit of force
Newton
CGS unit of force
Dyne
Acceleration formula
(v-u)/time
V is equal to
U + at
Force of friction occurs
Parallel
Value of g
9.8m/s square
Gravitational force of earth is called
Gravity
For a body moving downwards g is taken positive but in the other case negative
T
One newton is equal to how many kgf
.1 kgf
One newton = how many gf
100
1 newton = how many dynes
10 raised to5
Weakest and strongest force in nature
Gravitational and nuclear force
Force has how many main effects
4
Force formula
Mass x acceleration
Acceleration formula
Rate of change in velocity/ time
Squeezing a lemon is a
Balanced force
In equator acceleration due to gravity is
9.7 m/s square
In poles gravitational acceleration is
9.8 m/s square
Gravitational constant
G
G value
6.673 x 10 raised to -11 N m sq / kg sq
To calculate the force acted on a object by another object
F of gravitation = G x m1 x m2 / distance btw them squared
1 newton is equal to how many kgf and gf
.1 kgf and 100 gf
Solid particles in factory smoke are …………
charged
Solid particles in factory smoke is separated by
Electrodes
Electrostatic force is derived from a ………… word
Greek
Strongest force in nature
Nuclear force
Nuclear force ??????????????
The energy that binds the protons and neutrons in a nucleus
Momentum formula
Mass x velocity
Inertia?????????
The state of power within it to resist change in motion. Eg going forward when a train stops
Pressure in a water container
Increases with depth due to increase in gravity and weight acting on it
Pressure of water formula ( P)
P = density x gravity x height
What’s pascal’s law
When pressure is applied on a liquid,it is transmitted equally in all directions
Liquid pressure is measured by
Manometer
Barometer was discovered by
Torricelli
76 cm level high mercury indicates
1 atmospheric pressure
Spring balance use
Measure weight
Beam balance use
Measure mass
Impulse?????
Change in momentum when force is acted upon it for a short period of time. It is very short ( time)
Impulse formula
Force x time
What happens when you travel at the speed of light
Time remains constant it does not move
If u travel greater than speed of light
U can travel to the past
Albert Einstein discovered the formula
Energy possessed by an object = mass x c square
C stands for velocity of light
Muscular force also called
Mechanical force
Muscular force also called
Biological force
Gravitational acceleration on moon is
1.7 m/sec sq.l
Momentum formula
Mass x velocity
Impulse
Change in momentum
Impulse applied is equal to
Force x time
The SI unit of pressure that is pascal is named after
French physicist Blaise pascal
The average length of the atmosphere is
120 km
Name some magnetic materials
Iron , nickel , cobalt , aluminium,manganese, magnetite
Name 2 devices that are used to measure weight
Spring balance and compressed balance
Muscular force also called
Biological force
Gravitational force of the earth is called
Gravity
1 ATM is equal to
1.01 x 10 raised to 5 pascal
760 mm of Hg or 76 cm
760 torr
14.7 psi
Psi full form
Pound per square inch
1 inch is equal to
2.5 cm
1 pound is equal to
Half kg
1 pascal in charge unit is equal to
10 dyne / cm sq.
Colour of mercury
Silver
You cannot dive to more than a depth of
120 m deep in water
Pascals law states
The pressure exerted at any point in an enclosed liquid is transmitted equally in all directions
Mercury color
Silvery liquid metal
The buoyancy of an object can be calculated by the
Weight of the liquid displaced by the object when it is immersed in water.
How can you determine if the object on which the buoyancy is acted would float or sink
By using specific gravity
It is the ratio of the density of the object to the density of water.
If the specific gravity is-
More than 1 - it would sink
Less than 1 - it would float
How can you determine if the object on which buoyancy is acted would float or sink
By calculating specific gravity
It is the ratio between the density of the object to that of water.
If it is less than 1- it would float
If it is more than 1 - it would sink
Water has a specific gravity of
1
Density of water
1 gram / cm cube and 1000 kg / m cube
Buoyancy compensators helps you to get
Neutral buoyancy under water
3 types of buoyancy
Positive
Negative
Neutral
Positive buoyancy means
Floating
Negative buoyancy means
Sinking
Neutral buoyancy means
Half floating and half sinking
Perpendicular force is called
Thrust
Popping of ears happens to
Maintain the balance of pressure in your body
Venus atmospheric pressure is
90 times as that of earth due to the presence of CO2
Hydraulic machines include
Hydraulic jack,hydraulic brake
Hydraulic jack also called
Hydraulic lift
Oil is used in some hydraulic machines
To prevent rusting and to ensure smooth movement
To prevent back flow of fluid in the hydraulic jack there is a
Valve
1 atmospheric pressure is equal to 1
Bar
Momentum is equal to
Mass x velocity
Pulse is equal to
Force x time which is equal to change in momentum
Force x time is equal to
Mass x ∆velocity
The symbol stands for delta
Delta means change in something
Boyles law
V x P = n x R x T
Three types of barometer
Mercury barometer, Fortin’s barometer , aneroid barometer
Aneroid barometer speciality
Do not use mercury , do not need to be kept straight , an iron sheet within it is vaccuum , the iron sheet is situated
between a sealed metal box acts as the diaphragm , as pressure increases air presses diaphragm , and the wheel rotates in clockwise direction in a scale and totally vice versa
The disadvantage of aneroid s barometer is
Not accurate
Density of air at sea level
1.22 kg / metre cube
How does pressure decrease with altitude
For every 105 meter pressure would decrease by 1 cm of hg
Altimeter
An instrument in planes used to measure the altitude in relation with pressure.
With every 105 m there is a decrease in one cm of hg. Aneroid barometer is used in it
Fall in atmospheric pressure
Depression
Gauge vs barometer
Gauge is used to measure pressure in a closed container.
Barometer is used to measure atmospheric pressure
If water is replaced by mercury what is its height
10.34 metre
Mechanical advantage is
Load/effort
Kinetic theory of matter
Kinetic energy of molecules is directly proportional to absolute temperature
Molecules always attract each other.
2 types of attraction of molecules
Force of attraction between like molecules is called cohesive force
Force of attraction between different or unlike molecules is called adhesive force
In solids cohesive force is
Strong so they are held together
In gases cohesive forces are weak so what happens
They cannot be held to shape, no fixed rigidity , and no volume
As cohesive force is less in solids and liquids so ?
They can flow and have more freedom of movement. This property is called fluidity so liquids and gases are together called fluids
1 newton is equal to
10 raised to -5 newton = one dyne
1 newton = .1 kgwt = 100 gwt
Units of pressure
1 ATM = 1 bar = 10 raised to 5 Pa = 76 cm of Hg = 760 mm of hg = 760 torr
1 torr is equal to
1 mm of Hg
Buoyancy is also called
upthrust
If density is more in hares apparatus
Then the
Height of the liquid column will be shorter
So relative density of liquid is measured by
Haré apparatus using the formula
Height of water column / height of the liquid column
It is a ratio
Mercury barometer was discovered by and named after
Torricelli ( Torricellian barometer )
The empty space at the top in the barometer is called
Torricellian vacuum
Height of water if it is used instead of mercury in barometer
10.34 metre
Disadvantages of mercury barometer
Can be easily spilt
Impurities may dissolve
Fortin’s barometer advantage is
Can be measured accurately by using many scales
Plimsoll lines ?
It is a measuring index in ships to know the capacity it can safely carry within water
Mercury density
13.6 grams per cubic metre
In aneroid barometer the iron sheet is
Corrugated
Meniscus
A curved surface in a liquid
2 types of meniscus
Convex
Concave
Concave happens in
In water where cohesion force between molecules is less than adhesion between the container molecules
Convex meniscus happens in
Mercury where cohesion is more than adhesion
Surface tension ??????
The water molecules in the liquid have a force exerted by other water molecules around it. Thus they are placed in position.
But those molecules found on the surface are more free and form a stronger and more stable bond between them . This is called surface tension
What do you mean by law of conservation of momentum
The momentum of 2 bodies that collide remains same after their collision
M1 + M2 = M3 + M4
In elastic collision between objects
Law of conservation of momentum is followed
Maintain kinetic energy
In inelastic collisions between molecules do not follow
Kinetic energy is not maintained as some of kinetic energy transforms into internal energy
Density formula
Mass / volume
Specific gravity also called
Relative density
Specific gravity helps us to know
How much part of a solid floats on water and sinks in water
To find specific gravity of an object in a LIQUID
Density of object / Density of liquid (ratio)
The specific gravity of ice in water
Density of ice - 920
Density of water - 1000
So specific gravity is 920/1000 = .92
So 92 % of ice will sink in water and this is why you only see some part of an iceberg on top of water
Specific gravity has no unit as it is a
Ratio
Atmospheric pressure measured by
Barometer
Liquid pressure measured by
Pressure gauge , it’s simplest form is manometer which measures pressure difference.
Law of conservation of momentum
m1u1 + m2u2 = m1v1 + m2v2
CGS unit of work
erg
Work and energy are
Scalar qtys
Mechanical energy further classified into
Potential and kinetic energy
Centre of gravity of a right circular cone
Is situated h/4 distance from the base (height)
A body is said to be in equilibrium if
It does not experience any change in motion or rest , even under influence of outside forces
Mechanical efficiency of a machine
Output / input
OR
Work done by the machine / work done on it
Mechanical efficiency =
Mechanical advantage / velocity ratio
Velocity ratio of a simple machine
Ratio of displacement of power and load
In a lever , load arm ?
Distance of load from fulcrum
In a lever , effort arm ?
Distance of effort from fulcrum
Law of levers
Load x load arm = Power x power arm
Types of levers
1st order
2nd order
3rd order
1st order levers
Fulcrum comes between load and effort
E.g. seesaw , scissors
Second order levers
Load lies between fulcrum and effort
E.g. bottle lid opener
Third order level
Effort lies between fulcrum and load
E.g. forceps
Pulley
Simple machine used to alter the direction of force
3 types of equilibrium
Stable
Unstable
Neutral
Neutral equilibrium
A body is to be in neutral… if the height to its centre of gravity remains unchanged even when moved.
Unstable equilibrium and stable equilibrium
If the object changes it’s original position due to slight external forces and vice versa
Newton’s first law
Law of inertia
Newton’s second law
Force applied is directly proportional to rate of change of momentum
Newton’s third law
For every action there is an equal and opposite reaction
3 types of inertia
Inertia of rest
Inertia of motion
Inertia of direction
Mechanical advantage of a single fixed pulley
W/P = 1
Single movable pulley- mechanical advantage
W/P= 2P/P = 2
Block of pulleys mechanical advantage
If there are 6 pulleys in the total system then if -
The power applied is P
Then the work done is 6P ;using the formula the mechanical advantage is 6.
If there are ‘n’ no of pulleys then M.A.= n
Mechanical advantage of an inclined plane =
Length of plane / height of the plane
Fortin’s barometer
Improved form of mercury barometer
The Fortin’s barometer has
2 scales
Main
Vernier
Density of air
1.29 kg/m cube
Lift pump
Used to lift water using the principle of atmospheric pressure ( to a height of 10.34)
Bramah press or hydraulic press are applications of
Pascal’s laws
As the upthrust = weight of the fluid displaced ; it is directly proportional to
Volume and density of the fluid
Hydrometer
Device used to measure relative density of liquids
Bernoulli’s principle
Within a horizontal flow of fluid, points of higher fluid speed will have less pressure than points of slower fluid speed.
