Our Dynamic Universe Flashcards
Blueshift
Doppler-shifting of a light wave towards the blue end of the spectrum (observed frequency higher than emitted frequency) owing to relative motion of the source towards the observer
Components of a vector
two vectors which act at right angles, the vector sum of which is the original vector
Conservation of energy
energy cannot be created or destroyed, only converted from one form to another
Conservation of momentum
when two or more objects interact, the total momentum is conserved, in the absence of external forces
Dark energy
a theoretical form of energy postulated to act in opposition to gravity and to occupy the entire universe, accounting for most of the energy in it and causing its expansion to accelerate
Dark matter
thought to be a type of matter which does not interact with electromagnetic radiation so is invisible to astronomers detecting light or any other type of electromagnetic radiation eg radio to gamma
Displacement
a specified distance from a fixed point, in a specified direction. Displacement is a vector quantity.
Elastic collision
a collision in which both momentum and kinetic energy are conserved
Gravitational field
the region of space around an object in which any other object with a mass will have a gravitational force exerted on it by the first object
Gravitational field strength
the gravitational field strength at a point in a gravitational field is equal to the force acting per unit mass placed at that point in the field
Hubble’s law
Hubble’s law states that a galaxy’s velocity is proportional to the distance from the observer. Mathematically v = ho d where ho is the Hubble constant.
Impulse
the change of momentum of an object, equal to the product of the force acting on the object and the time over which the force acts
Inelastic collision
a collision in which momentum is conserved but kinetic energy is not
Instantaneous
at one point in time or at one particular instant in time
Kinetic energy
the energy of an object due to its motion
Momentum
the product of the mass of an object and its velocity. Momentum is a vector quantity, measured in kg m/s.
Newton
one newton is the force that, when applied to an object of mass 1 kg, will cause the object to accelerate at a rate of 1 m s -2 in the direction of the applied force
Potential energy
the energy stored in an object due to its position, its shape or its state
Projectile
a projectile is an object that is flying through the air under the influence of gravity. This means that the object is moving in two dimensions.
Redshift
Doppler-shifting of a light wave towards the red end of the spectrum (observed frequency lower than emitted frequency) owing to relative motion of the source away from the observer
Scalar
a physical quantity which has magnitude but no direction
Universal Law of Gravitation
also known as Newton’s law of gravitation, this law states that there is a force of attraction between any two massive objects in the universe.
Vector
a physical quantity which has direction as well as magnitude
Velocity
the rate of change of displacement. Velocity is a vector quantity.
Weight
the gravitational force acting on a mass
