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Physics Paper 1
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Gravity
Questions that I got wrong / reoccuring questions
Terms in this set (78)
Particle of mass m is moving with constant speed v in uniform circular motion. What is the total work done by the centripetal force during one revolution?
Zero
A cyclist rides around a circular track at a uniform speed. Net horizontal force at anygiven instant of time? (along direction of motion or perpendicular to it)
Along direction of motion - 0
Normal to direction of motion - non-0
A solid piece of metal melts into liquid without a change in temperature. What are the changes in the kinetic energy and potential energy of the molecules compared to those of the solid?
Kinetic Energy - SAME
Potential Energy - GREATER
Define heat
Energy that is transformed as a consequence of temperature differences (Kinetic energy of the particles).
Q=mcΔT (c=specific heat capacity)
Define Power
rate at which work is done or heat is released / electric potential energy transformed
Power= work / time
Power= heat / time
The first law of thermodynamics = principle of energy conservation
Energy cannot be created or destroyed. It can only change form.
Newton's first law
"An object at rest will remain at rest, and an object moving at a constant velocity will continue moving at a constant velocit, unless it is acted upon by an unbalanced force." Another name is Law of Inertia
Newton's second law
The change of motion of the body is proportional to the net force imposed on the body and is in the direction of the net force.
F = ma
Second law of Thermodynamics
thermal energy that flows from a warmer material to a cooler material
Refractive index
A measure of how greatly a substance slows the velocity of light OR, a measure of the light bending ability of a medium
n=sin i/sin r = v2/v1
Increasing no of harmonic is proportional to
increasing frequency
decreasing wavelength
1 eV = ?
1.60 x 10^-13 J
Light dependent resistor
A device whose resistance depends on the amount of light. An increase in light causes a decrease in resistance
Resistance increases as light intensity decreases, used for ambient light sensors
A coil of wire has a large number of turns. It is moved relative to a fixed magnetic field. The emf generated will be equal to:
The rate of change of magnetic flux linkage
A sinusoidal ac power supply has rmc voltage V and supplies rms current I. What is the maximum instantaneous power delivered?
2VI
Which of the following (alpha, beta, gamma, x-ray) causes the greatest number of ionizations as it passes through 1 cm of air? (total energy of ionizing radiation is the same)
Alpha
alpha - travels least, but most ionization
gamma - travels furthest but least dangerous
de Broglie wavelength
To any particle of momentum p, there corresponds a wavelength λ = h / p. Particles can show wavelike behaviour such as diffraction and interference. There is a 'probability wave' whose amplitude at a specific place gives the probability of finding the particle there.
Different nuclides spontaneously undergo radioactive decay, emitting either alpha, beta or gamma radiation. Which of the following correctly identifies all the emissions that do not have discrete energies?
beta
the rest- discrete
The design of a nuclear power station includes an electrical generator. The function of the generator is to convert:
Kinetic Energy to Electrical Energy
Which of the followin digital devices is least likely to use a charge couples device ( CCD ) in it construction (fax machine, camera, watch, x-ray machine)?
Watch
x-ray also captures image!!
A CD stores digital information with a series of bumps (lands) and pits. The depth of each pit is d. Which of the following is the most appropriate wavelength of laser light to recover the information? (d/2 , d , 2d , 4d)
4d
Least significant digit and most significant digit in a binary system
least - last most - first
Which quantities can be determined from a speed time graph of a particle travelling in a straight line?
distance travelled in a given time
+
magnitude of acceleration at a given instant
Correct statement of Newton's Second Law
Rate of change of momentum of a body is equal to the net external force acting on the body
Circular movement, constant speed
acceleration towards circle centre and velocity perpendicular to acceleration, in the direction of movement
Gravitational potential at a point =
work done per unit mass in moving a small mass from infinity to the point
What does the escape speed from the surface of the planet depend on?
radius + mass of planet
Definition of mole
Amount of substance that contains as many elementary entities as there are atoms in exactly 12 g of carbon 12
Ideal gas assumptions
negligible volume of gas compared to container, negligible intermolecular forces, constant random motion, collisions are perfectly elastic
The behaviour of a monoatomic gas such as helium will approximate to that of an ideal gas when it is kept at
low pressure - no ionization
Total energy of a closed system
constant
Value of wavelength found in the visible region of the electro-magnetic spectrum
blue - 400nm
red - 650-700nm
Resonance occurs when
Forcing frequency = Natural frequency
Which of the following wave phenomena (polarization, diffraction, refraction, doppler effect) is associated with blood flow measurements?
Doppler effect - movement
Optically active substance
A substance that rotates the plane of polarisation of light that goes through it.
Electro-motive force emf
E= delta flux/ delta time
power supplied by the cell per unit current from the cell
Schrodinger model
a model that treats electrons as matter waves, used math equation to describe the location of the electron in the hydrogen atom
Schrodinger model assumption
electron is described by wavefunctions
Diagrams only show real forces and centripetal is
not real, unbalanced
Vehicle driven uphill at constant speed. Energy changes:
chemical energy converted into gravitational otential energy, sound and thermal energy
Electric potential
In an electric field, it is the work done per unit charge q to bring that charge from infinity to point P. Units are J/Coulomb
V=W/q₀, W is work needed to move test charge
scalar
Electric potential gradient
when expressed in units of v/m,e
vector (gradient upwards/downwards)
In SHM
a proportional to negative displacement
Standing and travelling waves wavelengths
standing - twice the distance between consecutive nodes
travelling - distance between consecutive crests
Sunlight reflects from lake surface, reflected light is plane-polarized. Plane of polarization is
parallel to the lake surface
because all light in horizontal place is reflected
A test charge
Point charge which has no effect on the electric fiels in which it is placed
Raoul suggests that power losses in a transformer may be reduced by:
1. Using large diameter wire in the coils (more can flow)
2. Using wire of low resistivity (less energy wasted on heat)
In the Geiger-Marsden experiment alpha particles are scattered by gold nuclei. The experimental resuslts provide evidence that:
mosst of the mass and positive charge of an atom is concentrated in a small volume
Protons and neutrons are held together in the nucleus by
the strong nuclear force
The square of the amplitude of an electron wave function in an hydrogen atom is a measure of the
probability of finding an electron at a particular point
Statement asociated with the photoelectric effect
Electron emission is instantaneous
Which of the following energy sources (nuclear fission, wind energy, nuclear fusion, geothermal energy) results from the solar energy incident on earth?
Wind energy (hot air flows)
Likely to increase greenhouse gas concentrations in the atmosphere
Incineration of waste to generate electrical energy
Laser of wavelength a is used in a computer to read data from a cd. Depth of a pit on a CD?
a/4
Increasing the quantum efficiency of a CCD will increase:
1.signal strength
2.magnification
3.pixel size
4.resolution
1. Signal strength
A lift is operated by an electric motor. It moves between the 10th floor and the 2nd floor at a constant speed. One main energy transformation during the journey is:
Electrical to thermal!!
not potential to kinetic because of constant speed
A communications satellite is moving at a constant speed in a circular orbit around Earth. At any given instant in time the resultant force on the satellite is:
equal to the gravitational force on the satellite (resultant force is the "unreal force" which is the centripetal one here, thus the gravitational force)
A student is sitting on a chair. One force that is acting on the student is the pull of gravity. According to Newton's tird law, there must be another force which is:
the upward force on earth (not on chair)
Escape speed
The speed that a projectile, space probe, or similar object must reach in order to escape the gravitational influence of the Earth or Celestial body to which it is attracted.
Escape speed questions
work with energies
KE=PE
PE=mgh
KE=1/2mv^2
Unit for ratio: thermal capacity of a sample of copper/ specific heat capacity of copper
kg
Specific heat capacity
The energy required to raise a unit mass of a substance by 1 K.
Thermal capacity
The energy needed to increase the temperature of an object by 1K.
Latent heat
Heat absorbed or radiated during a change of phase at a constant temperature and pressure
In the kinetic model of an ideal gas it is assumed that:
a) The forces between the molecules of the gas and the container are always 0
b) The intermolecular potential energy of the molecules of the gas is constant
c) The kinetic energy of a given molecule of the gas is constant
d) The momentum of a given molecule of the gas is constant
b) The intermolecular potential energy of the molecules of the gas is constant=0
A positive amount of thermal enery Q is transferred to an ideal gas from its surroundings. The internal energy of the gas increases and the gas does a positive amount of work W on its surroundings. The change of state of the gas is:
a. isochoric
b. isobaric
c. isothermal
d. adiabatic
W is done by gas on surroundings -> V changes -> V/T constant -> P is constant
b. isobaric
Hooke's law
For an oscillating spring, the restoring force exerted by the spring is directly proportional to the displacement. That is, the more the spring is displaced, the stronger the force that will pull toward the equilibrium position. This law is expressed mathematically as F = -kx, where F is the restoring force and x is the displacement. The constant of proportionality, -k, is the spring constant.
Ammeter connects in
series
Voltmeter connects in
parallel
In order to reduce power losses in the transmission lines between a power station and a factory, two transformers are used. One is located at the power station and the other one at the factory. Correct types of transformers used?
1. Step up
2. Step down
Note: Transformers alter voltage. To have less current (I) for less losses, we need increased voltage ( I&V are inversely proportional). Step up increases voltage.
Half life
The time required for one half of the atoms of a radioactive substance to decay.
In the Schrodinger model of the hydrogen atom, the probability of fining an electron in a small region of space is calculated from the:
a. de Broglie hypothesis
b. Heisenberg uncertainty principle
c. (amplitude of the wavefunction)^2
d. rms value of the wavefunction
c. (amplitude of the wavefunction)^2
The radii of nuclei can be estimated from experiments involving
a. scattering of charged particles
b. the Bainbridge mass spectometer
c. emission spectra
d. beta particle spectra
a. scattering of charged particles
When a nucleus undergoes radioactive B+ decay, the change in the number of particles in the universe is:
a. 0
b. 1
c. 2
d. 3
c. 2
Green house gases
gases in the atmosphere that absorb and emit radiation within the thermal infrared range: Carbon Dioxide, Methane, Chlorofluorocarbons,Nitrous oxide
Transmit ultraviolet (from sun) radiation but absorb infrared radiation (heat given off by earth)
The rate of global warming might be reduced by
reducing the use of oil and coil with natural gases (less radiation, better efficiency)
The efficiency of a modern natural gas power station is aproximately
50%
Depth of a pit on a CD is
Wavelength/4
;