Forces CGP Flashcards
(49 cards)
what is scalar quantity
what is vector quantity
5 examples of each
magnitude only
magnitude + direction
scalar– speed, distance, mass, temp,time,
Vector-force,velocity,displacement,acceleration,momentum
what is a force
eg of contact force x4
eg of non contact forcex3
what is an interaction pair
push/pull that acts on object due to interaction w/ another object
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friction, air resistance, tension in rope,normal contact
magnetic,gravitational, electrostatic
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-pair of forces that r equal + opposite. Act on 2 interacting objects (3rd Law)
the unit for force
a contact force is when
a non contact force is when-
N
objects physically touching
objects physically separated
what is gravitational force
what does gravity attract
2 effects of gravity
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is it vector/scalar
force of attraction btwn masses
all masses
-makes everything fall to the ground on surface of planet
-gives everything weight
-vector
what happens when a force causes object to move through a distance
describe energy transfer involved when work is done
work is done on the object (energy transferred)
-to make object move, force must be applied
-thing applying force needs energy source
-the force does ‘work’ to move object, energy transferred from one source to another
-work is done whether energy transferred usefully/wasted
work done + energy transferred are the same thing
what is mass
what is weight
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What is the force acting on an object on earth caused by
when does gravitational field strength increase
-mass-amount of ‘stuff’ in object, stays same
-weight-force acting on object due to gravity(the pull of gravitational force
-gravitational field strength around earth
-closer to mass causing field
-stronger for larger masses
-weight of object affected by
-where does the weight of an object act from
-Describe this for an object with same density throughout- Uniform object
-what is used to measure weight
-what is used to measure mass
-Briefly describe relationship btwn mass + weight
gravitational field strength at point where object is
-single point, centre of mass
-centre of object
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-Newtonmeter (calibrated spring balance)
-mass balance
-directly proportional
Weight= Mass x Gravitational field strength
units for each
what happens if you double the mass of object
weight- N
mass- Kg
Gfs- N/Kg
weight doubles
what do sizes + arrows in free body diagrams show
where do the arrows come from
magnitude of forces + direction
centre of object
work done =force x distance
state units
Work done- J(oules)
Force- N(ewtons)
Distance- m
-one joule of work is done when
- 1 Joule=
force of 1 newton makes object move by 1 metre
1 Joule= 1 newton-metre
why do you need more than one force to stretch/compress/bend an object
-Work is done (energy is transferred) when a force stretches/compresses an object. How.
-what is elastic deformation
-what is inelastic deformation-
-what happens to the energy transferred to an object if it is elastically deformed
otherwise object would just move in direction of applied force
-forces also should be balanced
energy transferred to the elastic potential energy store of the object
-can go back to og shape + length when force removed
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-doesn’t return to og shape + length once force removed
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-ALL the energy goes to its elastic potential store
Force= spring constant x extension
state units and what extension means
-what does spring constant depend on
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F- Newtons
spring constant- N/m
Extension- m
extension can be extension or how much an objects been compressed
-spring constant depends on stiffness of material, stiffer material has greater spring constant
what is the relationship btwn force and extension
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-work done on the spring and elastic potential energy stored are = if
-the extension of an elastic object is …… to force applied if….
direct proportion
-spring has not inelastically deformed
-directly proportional if limit of proportionality has not been reached
what is limit of proportionality
maximum force , above it the extension is not proportional to force.
where graph curves down on force-extension graph OR curves up on extension-force graphs
describe rp investigating springs
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how would you work out weight of stone
-work out weight of masses using W=mg
-add pointer eg wooden splint to bottom of spring and top of spring on 0
-measure unstretched length of spring w/ metre ruler clamped to stand-( eye level )
-Add 1N weight, let spring come to rest. read position of pointer
-repeat 6 times - increasing masses
-work out extension caused: og length - each new length
-plot on graph- Force on y axis / extension on x axis
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-measure ext. of spring when stone hangs
-read weight off from graph
what does it mean when the line of best fit is straight in force-extension graph
-how would you work out K ( spring constant) in this scenario
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-what does it mean if graph curves
-gradient of line is k as Force= spring constant x extension
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-limit of proportionality reached- the spring stretches at uneven rate, more each time, even though same mass is added each time
Elastic potential energy= 0.5 x spring constant x (extension)”2
-what can u use this to work out
-elastic potential energy (j) in elastic deformation means 2 things-
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-area under graph in force-extension graph =
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-work done in stretching /compressing string (if limit of proportionality not reached)
-energy stored in spring
-energy transferred to spring as its deformed/ by string when returns to og shape
-the elastic potential energy store of stretched spring
what causes an object to rotate
what is a moment
Moment=forcexdistance
state units
-what distance is used
a force/system of forces
the turning effect of a force
moment- Nm
force- N
distance- m
-ALWAYS use distance perpendicular from the pivot to the line of action of the force
how do you get the maximum moment/turning effect when using a spanner
-why
-how can you increase moment
push at right angles to the spanner
-pushing at any other angle means smaller smaller distance so smaller moment
-larger force or longer perpendicular distance
how do you know if an object is balanced
-what equation do you use to find an unknown moment in a balanced object
total clockwise moment about a pivot= total anticlockwise motion about that pivot
-same equation as normal moment
what do levers do
-what do gears do
-what does turning one gear that is interlocked w/ another cause
-how do you increase the moment of a force in a gear / lever
a large …. will turn ……. than a small one
increase distance from the pivot at which the force is applied- reduces the force needed to get the same moment bcse moment=forcexdistance
-transmit rotational effect of a force from one place to another
-next gear turns in other direction
-use larger gear/ longer leaver
-large gear will turn slower than a small one
in physics a fluid is…
what does the pressure in fluids do
*how come particles in fluids exert
pressure
Pressure=Force/ Area
state units
liquid/gas
-exerts a force normal (at right angles) to any surface
-particles have mass and exert a force when they collide w/ an object
Pressure is force per unit area so particles exert pressure
Pressure- Pa
Force- Newtons
Area- m SQUARED
why in a liquid does the pressure at a point increase with the height of the liquid above that point 4 points
pressure = height of column x density of liquid x gravitational field strength
state units
-the density in a liquid is the same throughout.
-the more dense it is the more particle collisions so higher pressure
-as depth increases, no. of particles above the point increases.
-the weight of these particles causes pressure to the point
Pressure- pa
Height of liquid- m
density- KG/mCUBED
gravitational field strength- N/kg
