our Dynamic Universe Flashcards
Scalar quantities are described by
Magnitude only
Vector quantities are described by
Magnitude and direction only
Area below a velocity time graph is
Distance travelled
Initially at rest
U=0
Comes to a stop
V=0
Reaches maximum height
V=0
Accelerates due to gravity
A=9.8ms-1 downwards
Gradient of a displacement time graph?
Velocity
Gradient or a velocity time graph
Acceleration
Friction is
The force between two surfaces that opposes motion
The direction of friction is
Always in the opposite direction to the motion of an object
At rest means
No acceleration and forces are balanced
Constance velocity means
No acceleration therefore forced are balanced
The upward force of air resistance increases with
Downward force of velocity
Any vector quantity can be resolved into
2 perpendicular components
All moving objects have
Kinetic energy and momentum
Momentum is conserved in a collision as long as
No external forces act
If the collision is elastic
Total kinetic energy also conserved
If kinetic energy is not conserved the collision is
Inelastic
If two objects stick and collide
m1u1+m2u2=(m1+m2)v since velocity is the same
During inelastic collisions, energy is lost due too
Noise, heat and deforming materials
During explosions, what is conserved
Total momentum
Explosions are always
Inelastic as energy is added to the objects
Momentum equals
Mass times initial speed
Force times time equals
Change In momentum m1v1-m1u1
If force is constant, force times time equals
The area or the rectangle, impulse is the area below the force time graph
If force varies by time, impulse is the
Average force times time
The horizontal component of a projectile is
Constant velocity (we ignore air resistance)
The vertical component of a projectile is
Constance acceleration downwards true to gravity, equations of motion apply
If an object is orbiting around a planet, it is in
Free fall
What are Einstein’s postulates
The speed of light is the same for all observers
The laws of physics are the same in different frames of reference.
T’ is
Dilated time
Is dilated time (t’) bigger or smaller than proper time (t)
Bigger
L’ is the
Contracted length
What is bigger, contracted lenght (l’) or proper length (l)
Proper lenght
As the sound source move closer,
Waves closer together so frequency higher
As the sound source moves away
Waves further apart so frequency lowers
If the source is moving towards the observer
Subtract on the bottom line
If the source is moving away from the observer
Add on the bottom line
Light sources move away from us. Wavelength is increased this is called
Redshift
A light source moving towards us would be
Blueshifted
z
Redshift (no units)
The universe is
Moving apart
Dark matter
Energy that should be there but isn’t
Dark energy
Energy that increases the rate of the expansion of the universe
Hot objects emit radiation across a
Broad range of wavelengths
As surface temperature increases
More energy is emmited and the peak in the distribution is shorter wavelengths
Hubbles law evidence for expanding universe
Hubbles law suggests that universe began in same point 14 billion years ago and it is travelling in all directions outwards
Olbers paradox
The night sky is dari apart from points of light, if the universe was infinite, everything would be light
Cosmic microwave background radiation
Some of the energy in the Big Bang formed electromagnetic radiation, we can still obverse this radiation from all directions today.
