Unit 1:Our Dynamic Universe

Question 1

What is a balanced force?

Answer 1

Forces are balanced, no forces acting on the object.

Question 2

What is acceleration?

Answer 2

Rate of change of velocity.

Question 3

What is a scalar quantity

Answer 3

Only magnitude.

Question 4

What is a vector quantity?

Answer 4

Both magnitude and a direction.

Question 5

What is an elastic collision?

Answer 5

Kinetic energy is conserved and momentum.

Question 6

What is an explosion?

Answer 6

Two objects move apart during an explosion, the kinetic energy gained comes from stored energy in a spring or chemical.

Question 7

What is impulse?

Answer 7

Average force x time. The cause of change in momentum.

Question 8

What is an inelastic collision?

Answer 8

Kinetic energy is lost, momentum is conserved.

Question 9

What is the conservation of momentum?

Answer 9

Same value before and after a collision if no other forces are acting.

Question 10

State Newton’s 1st law.

Answer 10

Object will remain at rest or continue to travel at constant speed in a straight line-unless acted upon by an unbalanced force.

Question 11

State Newton’s 2nd law.

Answer 11

Unbalanced force acts on an object causing it to accelerate.

Question 12

State Newton’s 3rd law.

Answer 12

For every force there is an equal but opposite force.

Question 13

What is tension?

Answer 13

Pulling force applied by a string or cable on another object.

Question 14

What is friction?

Answer 14

Force that opposes the motion of all objects.

Question 15

What is a projectile?

Answer 15

An object that has both a horizontal and vertical component to its motion.

Question 16

What is a satellite?

Answer 16

An object in orbit around another.

Question 17

What is the frame of reference?

Answer 17

Background against which measurements are made.

Question 18

What is invariance?

Answer 18

Same for all observers in all observers in all frames of reference.

Question 19

What is a muon?

Answer 19

A sub-atomic particle with a short life.

Question 20

What are the postulates?

Answer 20

When two observers are moving at constant speeds relative to one another, they will observe the same laws of physics.
Speed of light in a vacuum is the same for all observers.

Question 21

What is Hubble’s law?

Answer 21

The further away from the Earth an object is, the faster it is moving away from the Earth. Only applies to very distant objects.

Question 22

What is Hubble’s constant?

Answer 22

Recessional velocity of an object divided by the distance from the Earth.

Question 23

What is recessional velocity?

Answer 23

Velocity at which a distant object is moving away from the Earth.

Question 24

What is red shift?

Answer 24

Spectra of all distant objects are shifted towards the red end of the spectrum, the faster an object is travelling away from the observer, the more it’s spectrum is red shifted.

Question 25

What is cosmic background radiation?

Answer 25

Observed background radiation present in every direction in the Universe, it provides strong evidence to support the big bang theory.

Question 26

What is dark energy?

Answer 26

Proposed to amount for the missing energy in the Universe and accounts or the fact that the rate of expansion is increasing.

Question 27

What is dark matter?

Answer 27

Proposed to amount for the missing mass of the Universe. Cannot be observed by conventional telescopes.

Question 28

What is a galaxy?

Answer 28

Large collection of stars.

Question 29

What is universal homogeneity?

Answer 29

Point of origin where all matter was spread out evenly across the Universe because it all happened at the same time.

Question 30

What is terminal velocity?

Answer 30

The velocity of an object when the driving force acting on it is balanced by the friction force.

Question 31

What is time dilation?

Answer 31

Time dilation is a difference in a time intervals measured by a stationary observer and a moving observer.