ODU Flashcards
Newtons first law states that
an object will remain at rest, or will continue to travel at a constant velocity unless acted on by an unbalanced force
Newtons second law states
A uniform unbalanced force ‘F’ applied to a mass ‘m’ will produce a uniform acceleration ‘a’ of the mass unless acted on by an unbalanced force. F=ma
Terminal velocity definition
he constant speed that a freely falling object eventually reaches when the resistance of the medium through which it is falling prevents further acceleration.
Forces on a slope:
How is the horizontal component calculated
Fh = Fcos0
Forces on a slope:
How is the vertical component calculated
Fv = Fsin0
Forces on a slope:
How is the parallel component of weight calculated
mgsin0
Forces on a slope:
How is the normal component of weight calculated
mgcos0
define power
the rate at which energy is converted from one form to another
Conservation of energy states that
Energy cannot be created or destroyed, only converted from one form to another
What is momentum
the product of mass and velocity
units of momentum
kg m ^-s
What is the law of conservation of linear momentum
The total momentum before a collision is equal to the total momentum after a collision, in the absence of external forces
Momentum is always conserved in a collision but ….
kinetic energy is nto always conserved
Elastic collision
momentum and kinetic energy are conserved
Inelastic collision
Momentum is conserved but kinetic energy is not
Describe how the force of an impact can be changed in terms of cars
Cars are designed with crumple zones at their front and rear. These specially designed areas absorb the energy of a collision, and increase the amount of time it takes for the car to come to a stop.
For a given change in momentum, the time of impact t increases. The effect of this is that the force of impact F acting on passengers is reduced. This increases the chance of surviving a serious accident
Similarly, for a given change in momentum, a softer surface will apply a smaller force than a harder surface. The softer surface can apply a smaller average force over a much longer period of time, as the material deforms more readily than the harder surface. This results in the same change in momentum, but with a much less damaging force.
Describe inverse square law in relation to gravitation
Beyond the surface of an object, the gravitational force decreases with increasing distance. The gravitational force varies inversely with the square of a the distance i.e. doubling the distance decreases the force by a factor of 4.
List the 2 variables that determine the gravitational force of attraction between 2 objects
the mass of the 2 objects and their distance apart
What is meant by Galilean invariance
Galilean invariance states that the laws of physics are the same whether you are stationary or moving at a constant speed
what are 2 postulates of special relativity
The laws of physics are the same for all observers; the speed of light is the same for all observers.
The speed of light must be the same for all observers. Name 2 consequences of this
Time dilation and length contraction
Identify the types of waves that display the doppler effect
Sound, light and all waves in the em spectrum
Does the observed frequency increase or decrease as the sound moves away from the observer
Observed frequency decreases
Does the observed frequency increase or decrease as the sound moves toward the observer
observed frequency increases
How does redshift affect the wavelength of light from distant galaxies
wavelength increases
what does redshift indicate about the motion of distant galaxies
that they are moving away from earth
What is meant by the recession velocity of galaxy
The velocity at which a galaxy is moving away from us
Hubbles’s law shows the relationship between which 2 quantities
Distance and the speed of a galaxy
what is causing the universe to continue expanding
Dark energy
List the colours of stars from the lowest to the highest temp
Red orange yellow white blue-white
How is the surface temp of a star determined
From the peak wavelength (colour emitted)
Describe what is meant by the cosmic microwave background
Radiation left over from the big bang that can be detected in all directions
what are the 2 most abundant elements in the universe
Hydrogen and helium
Give 2 reason why the night sky appears dark
Light from some galaxies will never reach us; redshift of visible light to non-visible wavelengths
What is happening to the rate of expansion of the universe
The rate of expansion is increasing
What is the ‘missing mass’ in galaxies referred to as
Dark matter
