Our Dynamic Universe Flashcards

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1
Q

Blueshift

A

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

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2
Q

Components of a vector

A

two vectors which act at right angles, the vector sum of which is the original vector

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3
Q

Conservation of energy

A

energy cannot be created or destroyed, only converted from one form to another

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4
Q

Conservation of momentum

A

when two or more objects interact, the total momentum is conserved, in the absence of external forces

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5
Q

Dark energy

A

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

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6
Q

Dark matter

A

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

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7
Q

Displacement

A

a specified distance from a fixed point, in a specified direction. Displacement is a vector quantity.

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8
Q

Elastic collision

A

a collision in which both momentum and kinetic energy are conserved

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9
Q

Gravitational field

A

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

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10
Q

Gravitational field strength

A

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

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11
Q

Hubble’s law

A

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.

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12
Q

Impulse

A

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

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13
Q

Inelastic collision

A

a collision in which momentum is conserved but kinetic energy is not

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14
Q

Instantaneous

A

at one point in time or at one particular instant in time

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15
Q

Kinetic energy

A

the energy of an object due to its motion

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16
Q

Momentum

A

the product of the mass of an object and its velocity. Momentum is a vector quantity, measured in kg m/s.

17
Q

Newton

A

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

18
Q

Potential energy

A

the energy stored in an object due to its position, its shape or its state

19
Q

Projectile

A

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.

20
Q

Redshift

A

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

21
Q

Scalar

A

a physical quantity which has magnitude but no direction

22
Q

Universal Law of Gravitation

A

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.

23
Q

Vector

A

a physical quantity which has direction as well as magnitude

24
Q

Velocity

A

the rate of change of displacement. Velocity is a vector quantity.

25
Q

Weight

A

the gravitational force acting on a mass