# questions that I got wrong Flashcards

A for ductile metal

D for rubber polymer

what happens when source of rays placed at focal length from lens

they have negative curvature cancelled out by positive curvature meaning you get parallel rays with the image at infinity distance

what happens when source of rays place at 2f from lens

as source moves from f to 2f, image is moving back from infinity so image which is huge at this point is getting smaller until at 2f image size = object size

between f and 2f image is really big which is why source placed at distance from lens in cinema projectors

so between f and 2f

you need avagadro constant as you have free electrons from each atom, molar mass, density

you can find moles from mass / molar mass

then moles * avagadro constant = total number of electrons

what is direction of electric field the same as

the direction of the electric field is the direction of movement of a positive charge

we are looking for electric field between plates so we’re using E=v/d to work out EFS and then F = Eq

how to use flemmings left hand rule to explain why charge moves in circle

thumb is direction of force

index is direction of field

middle is direction of charge

direction of force felt is at 90 degrees to direction of field so 2 forces make at move at 45 degrees, so it moves in a circle

when does %uncertainty add up

adds up all the time

when something is squared you double it

to find x think of conservation of energy

they gave us m and g so we can find h(x)

1/2kx² = mgx

inout and solve for 4

pv = 1/3nmc² (c is mean square speed)

rearrange for v = (nm / 3p) c²

brackets is constant

if you doubled the mean square speed, v doubles

stability of protons and neutron

decay equations where applicable

neutron is unstable so turns into proton

protons stable on their own but not in nucleus

n -> p + e- + antineutrino

what is the grad of flux linkage graph

gradient is negative emf

gradient of flux linkage is negative emf

0 to t_{0} there’s a constant flux induced so a constant emf is induced so nothing is changing so grad doesn’t change

t_{0} to time no change in grad so no emf induced

answer is d

2 sources of equal mass so N0 is constant

to find ratio N = N_{0}e^{-}λ^{ * t} / N_{0}e^{-}λ^{ * t}

N0 is constant so e^{-}λ^{ * t} / e^{-}λ^{ * t}

can get λ from Log2 / T_{1/2}

input data to get 2

Q2: A = λ N

A1 / A2

we worked out N = 2

A = log2 / 15 / log2 / 10 * 3 = 4/3