Our dynamic universe Flashcards
Scalar
A quantity defined by its magnitude
Vector
A quantity defined by both its magnitude and its direction
Where a scalar has distance a vector has
Displacement
Where a scalar has time a vector has
Velocity
Where a scalar has speed a vector has
Acceleration
Where a scalar has energy a vector has
Force
Where a scalar has mass a vector has
Momentum
Distance
The distance an object has traveled is simply a measure of how far the object travels.
The direction is irrelevant
Where a scalar has displacement a vector has
A measure of how far the finlay point is from the starting point
Has magnitude and direction
Speed=
Distance
Time
Velocity
Displacement
Time
Acceleration
The rate of change in velocity
Time taken
U=v-a
T
Acceleration is measured in…
Meters per second
Ms^-2
Newtons first law
An object will remain at rest or continue to move at a constant speed (in a straight line) unless acted upon by an unbalanced force
What are the consequences of newtons first law
Constant speed (including stationary)= balanced forces Acceleration must involve unbalanced forces
Forces are balanced if….
They are equal in size but opposite in direction
Newtons second law
F=ma Where F= unbalanced force in newtons (N) M= mass in kg a= acceleration
In F=ma if m increases….
a decreases
In F=ma if F increases…
a increases
Newtons third law
Concerning equal forces, If A exerts a force on B, then B exerts an equal but opposite force
Distance
The total path length described by magnitude alone
Displacement
Is the direct length from a starting point to a finishing point
To describe displacement both magnitude and direction must be given
Average velocity
Displacement
Time
Velocity has….
Magnitude and direction
Displacement and velocity have direction as well as magnitude and are hence….
Vectors
Distance and speed do not have direction but do have magnitude and are hence…
Scalars
In a velocity time graph, displacement is….
The area under
In a velocity time graph, acceleration is….
The gradient
In equations, S stands for…
Displacement (m)
In equations, U stands for…
Initial velocity (ms^-1)
In equations, V stands for…
Final velocity (ms^-1)
In equations, A stands for…
Acceleration (ms^-2)
In equations, T stands for…
Time (s)
V=..
U+at
S=…
Ut+1/2 at^2
When adding two vectors in the same direction together the resultant is equal to….
Their sum
When adding two vectors in the opposite direction together the resultant is equal to….
Their differences
In F=ma what is F
The resultant or unbound force measured in newtons, N
In F=ma what is m
The mass in kilograms, kg
In F=ma what is a
The acceleration measured in meters per second per second, ms^-2
In W=mg what is W
The weight measured in neutrons
In W=mg what is m
The mass measured in kilograms, kg
In W=mg what is g
The gravitational field streangth in newtons per kilogram, Nkg ^-1
Unbalanced force =
Thrust-frictional forces
When a person stands on a scale the reading is…..
The force the scale exerts toward the person to support the persons weight
When a person on a scale experiences acceleration….
It will change to the force between the person and the scale
Objects are known to accelerate down inclined planes because of…
An unbalanced force
Momentum
Mass x velocity
(P=mxv
Momentum is measured in
Kgms^-1
Is momentum vector or scalar
Vector
The law of conservation of momentum
When two objects collide the total momentum/explosion before the collision is equal to the total
momentum/explosion after the collision in the absence of external forces
Impulse
FxT
Impulse is measured in …
Neutons per second Ns
The area under a force time graph corresponds to…..
The change in momentum, the impulse
Newtons law of gravitation
M1m2
F=G——-
r^2
Universal constant of gravitation
6.67x10^-11m^3kg^-1s^-2
Special Relativity
Explains hie space snd time are linked for objects that are moving at a constant speed in a straight line
the speed of light in a vacuum is the same for all observers
Time dilation
Due to the effects of special Relativity the moving clock measures a shorter time than the stationary clock
Time dilation equation
t
t’=—————-
|—————
| 1-(v/c)^2
The Doppler effect
The apparent change in frequencies of a wave caused by relative motion between the sound wave and the observer
Formula for the doppler effect
V
f.=f,(—————-)
|—————
| v +/- Vs
Due to the doppler effect, if the source of a sound is moving towards an observer….
The frequency increases
The wavelength decreases
Due to the doppler effect, if the source of a sound is moving away an observer….
The frequency decreases
The wavelength increases
Hubbels Law
V=H•d
In hubbels law v is…
The velocity of a receding galaxy
In hubbels law d is…
The distance to the galaxy
In hubbels law H• is…
Hubbels constant
2.3x10^-18s^-1
Dark matter
Galaxies seem to rotate too quickly for the mass of their stars
Suggests that there is mass in the universe that is invisible to instruments used by scientists
Know it is there because it has gravity that affects objects nearby
Must make up 21% of the universe
Dark energy
Galaxies are moving away increasingly faster. The expansion of the universe is accelerating
Scientists do not understand how this could happen but have come up with dark energy
Must make up 74% of the universe
The higher the temperature of an object…..
The shorter the peak wavelength of its spectrum
Which is hotter blue or red stars
Blue
Hotter objects emit….than cooler objects
More radiation per unit area per unit time t
Describe evidenced supporting the Big Bang theory
Cosmic microwave background radiation
The abundance of hydrogen and helium
The darkness of the sky ( obleis paradox
The large number of galaxies showing redshift rather than blue shift
