Unknown areas Flashcards
Explain that consideration of centripetal (radial) acceleration as the rate of change in linear (tangential) velocity leads to?
The concept of a centripetal (radial) force required to maintain circular motion.
State what is meant by the moment of a force
A measure of its tendency to cause a body to rotate about a specific point or axis.
What is Torque defined as?
The product of radius and force applied at that radius to an axis of rotation.
Define the moment of inertia, I, of an object as?
A measure of its resistance to angular acceleration about a given axis.
Describe the principles of the Cavendish/Boys and Maskelyne Schiehallion experiments.
Cavendish - measuring Earth’s density (and thus its mass) but also for proving that Newton’s law of gravitation worked on scales much smaller than those of the solar system.
The Schiehallion experiment was an attempt to measure the mass of the earth using a pendulum and a mountain (Mount Schiehallion). The mass of the mountain was approximated and the deflection of a pendulum due to the gravitational force of the mountain was measured.
Describe a Gravitational potential ‘well’.
The term “well” is used to describe the shape of the curve created by the gravitational potential of a body. The deeper the well, the more energy that a mass must have in order to leave the gravitational pull of the large body.
Explain why smaller planets have no atmosphere and the low incidence of helium in Earth’s atmosphere etc.
Planets with smaller masses, like that of Mercury, or even Earth, don’t have enough gravity to hold onto the lighter gases, like Hydrogen and Helium. These gases can escape the gravitational pull of the planet and drift off into space.
Describe the consequences of the Equivalence Principle?
- Clocks in non-inertial reference frames e.g. accelerating spacecraft
- Clocks at altitude i.e. clocks run at different speeds in different
gravitational field strengths - Precession of Mercury’s orbit
- Gravitational lensing of light
What is spacetime?
A representation of four dimensional space.
Light or a freely moving object follows what kind of path?
A geodesic (the shortest
distance between two points) path in spacetime.
What curves spacetime?
Mass
Where does gravity arise from?
The curvature of spacetime
Where are stars born?
Stars are born in interstellar clouds that are particularly cold and
dense (relative to the rest of space).
What are the challenges to classical theory by considering experimental observations that could not be explained by classical physics?
- Black-body radiation curves (“ultraviolet catastrophe”)
- Planck’s suggestion that the absorption and emission of
radiation could only take place in ‘jumps’, - photoelectric effect could not be explained using
classical physics, - Einstein’s suggestion that the energy of electromagnetic
radiation is quantized, - The Bohr model of the atom, which explains the
characteristics of atomic spectra in terms of electron
energy states, Bohr’s quantisation of angular
momentum, - De Broglie suggested that electrons have wave
properties, the de Broglie relationship between
wavelength and momentum and electron diffraction is
evidence for wave/particle duality.
Describe of the effects of damping in SHM (to include underdamping, critical damping’ and overdamping)
An overdamped system moves slowly toward equilibrium. An underdamped system moves quickly to equilibrium, but will oscillate about the equilibrium point as it does so. A critically damped system moves as quickly as possible toward equilibrium without oscillating about the equilibrium.
