Topic 1 Working as a Physisist Flashcards
Precautions to improve accuracy in an experiment [2]
[1] read at eye level to reduce parallax errors
[1] check for zero errors on measuring equipment to reduce systematic errors
Benefit to using data logger [1]
[1] Readings are simulations
Or
[1] Higher sampling rate
Explain how a graph is not directly proportional [1]
[1] line does not pass through the origin
Explain increased resistance with temperature in metals [4]
[1] As temperature increase the (lattice) ion/atom vibrations increase
[1] (for the same current) electrons will collide more frequently with the vibrating (lattice) ions/atoms
[1] More energy dissipated by collisions so (for constant I) greater V required
Or (constant V gives) lower v and, since I = nAvq, I will be lower
[1] Since V increases and R = V/I, R will increase with temperature
Or Since I decreases and R = V/I, R will increase with temperature
Graphical proof for absolute zero [2]
[1] Extending/extrapolating the line backwards
[1] The volume occupied by a gas will be zero at a particular temperature
Or
[1] The graphs for different gases
[1] All cut the x-axis at the same temp
Which is more accurate for measuring velocity at the end: measuring distance travelled every second (A) rather than total distance travelled divided by total time (B) [1]
[1] A (Can be implied within the answer)
The idea that the time increments are smaller Or the idea that the velocity is (constantly) changing
Or
[1] Not B(Can be implied within the answer) As B gives the value over the whole journey Or B does not take into
account that the velocity of the battery is (constantly) changing
Sources of error and changes when using: a measuring tape and a manual stopwatch [3]
Source of error:
[1] (Human) reaction time Or recording the exact position of the battery at the correct time Or parallax when marking the position of the battery
Changes to the method:
[1] Film/video camera
[1] with a measuring tape/scale along the ramp (and watch frame by frame)
Or
[1] Motion sensor
[1] Connected to a computer/data logger (to directly plot/record distance against time)
Or
[1] Strobe (as a timer)
[1] Set with a frequency of 1 Hz (or any sensible frequency suggested with a reason)
When asking for displacement two things need to be given: [2]
[1] magnitude
[1] direction
Explain the difference between scalar and vector quantities [1]
[1] scalar - magnitude/size only but vector -magnitude/size and direction
“However fast I run, my average velocity for the lap will be zero”.
Comment on his statement. [3]
[1] velocity is: a vector / speed in a given direction / = displacement/time
Or
velocity = (total distance in a particular direction)/time
[1] end and start at the same place
Or
distance in any direction is zero
Or
displacement = 0
[1] Therefore true as average velocity is zero (0 divided by any number is 0) (v=d/t=0/t)
Explain total internal reflection in an object [4]
[1] The light strikes the sides at an angle greater than the critical angle
[1] It undergoes total internal reflection
[1] It reflected again
[1] It strikes the other end at less than the critical angle
Or
It is transmitted at the final boundary
Or
the ray has zero angle of incidence at the first end and is transmitted un-deviated
Describe and explain the change in the resistance of the bulb as the potential difference across it is increased. [4]
[1[ The resistance increases
[1] (Because) the temperature increases (accept heats up)
[1] Increasing the amplitude of the oscillation of the lattice ions
[1] Leading to more (frequent) collisions of electrons with lattice ions
Explain how stationary waves are formed [3] e.g on a string
[1] Waves from the generator are reflected at the end
Or waves are travelling in both directions
[1] (When the two) waves (meet they) superpose/undergo superposition
[1] Producing points where the waves are in phase and points where they are in antiphase
Or producing points of zero amplitude and points of maximum amplitude
Or
producing nodes and antinodes
Why can you touch a node without disturbing the wave [2]
[1] Point is a node, so zero amplitude OR Point is a node, so string not moving
[1] So no energy absorbed
Or
Waves continue to move after superposition
Disadvantage of measuring off a low-resolution scale [1]
[1] Lack of precision (scale related) Or Lack of accuracy (output related)
