Year 12 physics definitions topic order Flashcards
Scalar
A scalar quantity is one which has magnitude but not direction.
Vector
A vector quantity is one which has both magnitude and direction.
Vector triangle
A vector triangle is a type of scale diagram with two vectors drawn tip-to-tail, to show how they can be added together.
Resultant vector
The vector sum of two or more vectors.
The components of a vector
The components of a vector are the parts of a vector in two perpendicular directions.
One Newton
One Newton is the force needed to give a mass of 1 kg an acceleration of 1 metre per second squared.
Equilibrium
Objects are in equilibrium when all the forces acting on them in the same plane (coplanar forces) are balanced - there is zero net or resultant force.
The moment of a force
The moment of a force (or turning moment) is the product of the force and the perpendicular distance of its line of action from the pivot or axis.
The principle of moments
The principle of moments states that for an object to be in rotational equilibrium, the sum of the clockwise moments must equal the sum of the anti-clockwise moments.
Torque
Torque is the moment of a couple. The torque of a couple is the product of one of the forces and the perpendicular distance between them.
Centre of mass
The centre of mass of an object is the single point at which all of the mass of the object can be assumed to be situated.
Density
The density of an object is its mass per unit volume.
Archimedes’ principle
Archimedes’ principle states that the upward buoyant force (upthrust) exerted on an object immersed in a fluid is equal to the weight of the fluid displaced.
Work done
The work done, or energy transferred, is the product of the force and the distance moved by the force in the direction of movement.
A closed system.
A closed system is any system in which all the energy transfers are accounted for.
Energy or matter cannot enter or leave a closed system.
The principle of conservation of energy
The principle of conservation of energy states that the total energy of a closed system remains constant. Energy cannot be created or destroyed, it can only be transferred from one form to another.
Elasticity
Elasticity is the property of a body to resume its original shape or size once ethe deforming force or stress has been removed.
Hooke’s Law
Hooke’s Law states that the extension of an object is proprtional to the force that causes it, provided that the elastic limit is not exceeded.
Stress
Stress is force per unit cross-sectional area. It has unit Nm-2 or Pa and the symbol σ
Strain
Strain is extension per unit length. It has units and is therefore dimensionless.
Ductile
A ductile material can be drawn into wires and will show plastic deformation under tensile stress before breaking.
Malleable
A malleable material can be hammered or beaten into flat sheets and will show extensive plastic deformation when subject to compressive forces.
Brittle
A brittle material will break with little or know plastic deformation.
Hard
A hard material will resist plastic deformation by surface indentation or scratching.
Stiffness
Stiffness is the ability of a material to resist a tensile force.
Polymer
A polymer is a material made of long chains of molecules.
Ultimate tensile strength
Ultimate tensile strength is the maximum stress a material can withstsnad while being pulled or stretched, before it fails or breaks.
Young modulus
The Young modulus is the ratio of stress/strain for a given material.
Newton’s first law
A body will remain at rest or continue to move in a straight line at a constant velocity unless an external force acts on it.
Newton’s second law
The resultant force on 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.
Newton’s third law
If object A exerts a force on object B, then object B will exert an equal and opposite force on object A.
Impulse
Impulse is the product of force and the the time for which the force acts.
Elastic collision
An elastic collision is one in which both the momentum and kinetic energy are conserved. No energy is transferred to other forms.
Inelastic collision
An inelastic collision is one in which the momentum is conserved but some of the kinetic energy is transferred to other forms.
