things to remember

Question 1

how does centripetal acceleration come about

Answer 1

Due to the gravitational force and contact force acting on it, they are in opposite directions and the resultant causes centripetal acceleration

Question 2

why is the path of an object in orbit circular

Answer 2

the centripetal force is given by gravitational force which is perpendicular to velocity and causes centripetal acceleration

Question 3

what happens when two like charges are put next to each other and they are able to move

Answer 3

-they repel each other
- their velocities are equal and opposite (COM)
- force decreases with distance so their acceleration
decreases

Question 4

when drawing a graph of induced emf from flux density

Answer 4

The peak is where the gradient of the flux is steepest and when gradient =0 emf is 0

Question 5

why doesn’t an electron follow a circular path when in a uniform electric field

Answer 5

-the force is not always perpendicular to velocity
- or force isn’t always in the same direction

Question 6

why do dark lines when white light passes through a cloud of cool gas

Answer 6

-photons have discrete energy due to their wavelength
- match with one electron exciting it goes to a higher energy level
-electron de-excites emitting a photon in any direction causing the dark lines

Question 7

how to calculate power in radioactivity

Answer 7

activity x energy in joules

Question 8

what can be concluded about the universe due to an observed change in wavelength

Answer 8

objects are moving away,
-the universe is expanding
- the wavelength has increased due to redshift

Question 9

why might the total amount of energy released in a decay process be greater than the calculated answer

Answer 9

gamma photons are also emitted
- the product has kinetic energy to conserve momentum

Question 10

how do you calculate the energy needed to move a moving object from obit to infinity

Answer 10

Gravitational potential energy - kinetic energy

Question 11

how does the value of mean power differ between full wave and half wave rectification

Answer 11

half wave is half full wave value

Question 12

why might the transmitted intensity through a sample of two mediums be less than the calculate answer

Answer 12

• ultrasound is absorbed and reflected by matter in the medium
  -there is more than one boundary so more reflectionswha

Question 13

what can be concluded from the diffraction pattern of electrons about their nature

Answer 13

the beams spread which indicate diffraction and show they are wave like

Question 14

if electrons are accelerated through a greater p.d. how would that change the diffraction pattern

Answer 14

-wavelength is inversely related to momentum
-increase in p.d. increases speed and momentum
-wavelength decreases causes a smaller diffraction angle

Question 15

explain why at the surface of the sphere gravitational field is negative to displacement

Answer 15

g is always attractive
force is opposite direction to displacement

Question 16

how can the surface temperature of a distant star be determined from the wavelength spectrum of the light from the star

Answer 16

-wavelength is inversely proportional to temperature
-using the peak wavelength emitted by the star
-have the wavelength of peak intensity from an object of known temperature determined

Question 17

what does the root mean square mean?

Answer 17

<c^2> means the mean square speed.
if told to find the root mean square speed (rms) just square root the value of <c^2>