# OCR A level Physics Flashcards

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Resultant force
a single force which has the same effect as the sum of all the forces acting on the body
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Newton
the force that causes a mass of 1kg to have an acceleration of 1ms^-2
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Terminal velocity
when the upwards force becomes equal to the weight of a falling object which cause it's resultant force to be zero
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Equilibrium
when all the forces acting on an object (coplanar forces, acting on the same plane) are balanced
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Moment of a force
the product of a force and the perpendicular distance of its line of action
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Principle of moments
the sum of the clockwise moments is equal to the sum of the anticlockwise moments
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Conditions for equilibrium to take place
resultant force = 0 //principle of moments
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Couple
when two equal, antiparallel forces act to produce a rotation
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Torque
the product of one of the forces of a couple and the perpendicular distance between them
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Centre of mass
the single point at which all the mass of the object can be assumed to be situated
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Density
mass per unit volume // kgm^-3
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Archimedes' principle
the upward buoyant force exerted on the object immersed in a fluid is equal to the weight of the fluid that the object displaces
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Work
the product of the force and the distance moved by the force i the direction of movement
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Principle of conservation of energy
the total energy of a closed system remains constant, energy cannot be created or destroyed. Only transferred from one form to another.
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Power
rate of doing work // watts
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Elasticity
property of a body to resume it's original shape/ size once the deforming force has been removed
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Deformation
the change in shape or size of the object // elastic = returns to original shape // plastic = remains in new state
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Hookes' Law
the extension of an object is proportional to the force that cause it, provided the elastic limit is not exceeded
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Stress
force per unit cross-sectional area //Nm^-2 or Pa
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Stress
extension per unit length
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Ductile
material can be drawn into wires and will show plastic deformation under tensile stress before breaking
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Malleable
material can be hammered or beaten into flat sheets and will show extensive plastic deformation when subjected to compressive forces
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Brittle
will break with little or no plastic deformation
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Hard
will resist plastic deformation by surface indentation or scratching
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Stiffness
property: resist tensile forces
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Polymeric material
made up of long chain molecules called polymers
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Ultimate tensile strength
maximum stress a material can handle while being pulled or stretched before it breaks
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Newtons' First Law
A body will remain at rest or constant velocity unless an external force acts on it
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Newtons' Second Law
The resultant force of an object is proportional to the rate of change of momentum of the object, and the momentum change takes place in the direction of the force
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Newtons' Third Law
If object A exerts a force on object B, object B will exert an equal and opposite force on object A
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Principle of conservation of momentum
the total momentum before a collision is always equal to the total momentum after the collision, provided that no external forces act on it
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e.m.f
Electromotive supply: a supply of energy gained per unit charge by charges passing through
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p.d
the energy transferred per unit charge by the charges passing through the component
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Ohms' law
the current through the conductor is directly proportional to the p.d, provided that the temperature remains constant
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1kWh
3600 000J
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Conservation of charge (Kirchhoff's first law)
the algebraic sum of the charges in a circuit must equal zero
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Kirchhoffs' second law
the e.m.f provided by the cell must be the same as the total drop in pd across all of the resistors in a loop
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Internal resistance
(in a source of e.m.f) is the resistance to electric current of the materials inside
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Intensity of a wave
the rate at which energy is transferred from one location to another
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Plane-polarised wave
oscillations of the field and the direction of travel are confined to a single plane
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Polarising filter
produces plane polarised light by selective absorption of one component of the incident oscillations - the filter transmits only the component of light polarised perpendicular to that direction
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Quantum
a small discrete unit of energy
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Electronvolt
the KE gained by an electron when it accelerates through a p.d of 1 volt
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Work function (of a metal)
minimum amount of energy required to just release an electron from its surface
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## Other cards in this set

### Card 2

#### Front

the force that causes a mass of 1kg to have an acceleration of 1ms^-2

Newton

### Card 3

#### Front

when the upwards force becomes equal to the weight of a falling object which cause it's resultant force to be zero

#### Back ### Card 4

#### Front

when all the forces acting on an object (coplanar forces, acting on the same plane) are balanced

#### Back ### Card 5

#### Front

the product of a force and the perpendicular distance of its line of action

#### Back 