Our Dynamic Universe

Question 1

Blueshift

Answer 1

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

Question 2

Components of a vector

Answer 2

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

Question 3

Conservation of energy

Answer 3

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

Question 4

Conservation of momentum

Answer 4

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

Question 5

Dark energy

Answer 5

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

Question 6

Dark matter

Answer 6

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

Question 7

Displacement

Answer 7

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

Question 8

Elastic collision

Answer 8

a collision in which both momentum and kinetic energy are conserved

Question 9

Gravitational field

Answer 9

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

Question 10

Gravitational field strength

Answer 10

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

Question 11

Hubble’s law

Answer 11

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.

Question 12

Impulse

Answer 12

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

Question 13

Inelastic collision

Answer 13

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

Question 14

Instantaneous

Answer 14

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

Question 15

Kinetic energy

Answer 15

the energy of an object due to its motion

Question 16

Momentum

Answer 16

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

Question 17

Newton

Answer 17

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

Question 18

Potential energy

Answer 18

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

Question 19

Projectile

Answer 19

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.

Question 20

Redshift

Answer 20

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

Question 21

Scalar

Answer 21

a physical quantity which has magnitude but no direction

Question 22

Universal Law of Gravitation

Answer 22

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.

Question 23

Vector

Answer 23

a physical quantity which has direction as well as magnitude

Question 24

Velocity

Answer 24

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

Question 25

Weight

Answer 25

the gravitational force acting on a mass