Hey there! Sign in to join this conversationNew here? Join for free
    Offline

    2
    ReputationRep:
    To have done it from the bank you would need a new resistive force from yhe rock because the boy adds weight downwards....it could have been done possibly but was much jarder that way
    Offline

    9
    ReputationRep:
    (Original post by gasman95)
    Seen a few people here mention that the initial gradient of the truck (e.g. the acceleration)
    would be greater. Surely, as the question stated that the water flowed out continuously across the entire journey, so therefore the initial mass would be the same and hence the same initial gradient as before.
    Yep I put the line so that it started like the initial gradient then increased. Did you draw a line with gradient continuously increasing to the very end? I thought it said that the water will flow for all the time given on the graph
    Offline

    2
    ReputationRep:
    (Original post by micycle)
    This is how I drew it:

    Oh damn! i did this, but i did a straight line coming out instead of it refracting
    Offline

    2
    ReputationRep:
    (Original post by WillRose)
    absolutely horredous exam

    for the 6 marker i said the speed would end up greater as fricton between the tyres and the road is proportional to the reaction force, less reaction, less friction, greater end speed
    Yeah i put this also....dont see why its wrong it makes perfect sense
    Offline

    3
    ReputationRep:
    Also the question said that total resistive force is proportional to its mass, so decreasing mass means decreasing resistive force and since driving force is constant, driving force is then bigger than resistive force which causes it to accelerates. I then wrote eventually all the water flowed out and everything is back into equilibrium again
    Offline

    19
    ReputationRep:
    Im depressed ffs
    Offline

    7
    ReputationRep:
    swear the boy can stand on it? if you take moments about the end of the plank(one not on embankment) and do at a point of tilting around the rock senario the wieght of the plank and its distance from rock is grater than the wieght of the boy and his distance from rock so he can
    Offline

    3
    ReputationRep:
    (Original post by mbh16)
    oh ok, but yeah the driving force is constant but the resultant force won't be cause of air resistance?
    It said total resistive force, so I assumed they had air resistance included
    Offline

    2
    ReputationRep:
    (Original post by Billsonbubbles)
    Cheers !

    I stated the CW and ACW moment and said that as the rock provided the CW moment and the ACW came from the boy and the weight of the plank the CW was larger hence he could not walk to the end
    oh right, i said that he could but everyone that did it your way said he couldn't and everyone that worked out the moment about the rock said he could
    Offline

    0
    ReputationRep:
    I got exactly the same
    Offline

    0
    ReputationRep:
    M


    Posted from TSR Mobile
    Offline

    2
    ReputationRep:
    (Original post by Nerrad)
    It said total resistive force, so I assumed they had air resistance included
    oh right ok so how did u draw the graph?, cause it said that u could use the graph to explain
    Offline

    1
    ReputationRep:
    It was ok, just had problems with time management, they really wanted to **** us hard
    Offline

    9
    ReputationRep:
    What did you guys get for the max vertical height in the projectile motion question?
    Offline

    0
    ReputationRep:
    First time I've ever not finished an exam. I finish every phya2 paper I've done as revision 10 minutes early at least, this one I had to rush the last two questions (my strongest topics) and had to guess with no calculations the light in diamond diagram. Will be lower than 48 for an A judging by the comments on here. Assuming that we're stronger students than the average based on the fact that we care enough to look up the exam before and after, I'm going to say roughly 45 for an A, wouldn't be lower than 43 though I assume because 42 would be 60% and it is a bit ridiculous to say 60% for an A. I'm very strong on phya2 but I'd be surprised if I get over 50 marks, probably 46ish. I luckily revised centre of mass and Vx=Vcos(feta) as I had a strong suspicion they'd come up with it being last exam, and them not coming up before I believe, but I was very dumbfounded at the spring, and projectile questions because they were so different, and the 6 marker was definitely something I dropped serious marks on. Spent 10 minutes on it at least, probably more and only have got 4 marks max, probably 2-3. But as the old AQA motto goes, "Fail to prepare, prepare to fail. Prepare, prepare to fail."
    Offline

    0
    ReputationRep:
    (Original post by gasman95)
    Seen a few people here mention that the initial gradient of the truck (e.g. the acceleration)
    would be greater. Surely, as the question stated that the water flowed out continuously across the entire journey, so therefore the initial mass would be the same and hence the same initial gradient as before.

    yeah i put the initial gradient as the same, but said the the acceleration would continue increasing for a longer period, and my sketch on the graph had the same initial gradient and stayed steeper than the other gradient for longer, until it reached a constant velocity, a bit higher up than the lorry without the leak.
    Offline

    0
    ReputationRep:
    The embankment one:

    R (Reaction force at embankment) = 0
    Resolve from the rock.
    Vertical force at the left much be greater than the right for the boy to stand without falling

    Mass of boy = 46kg Distance to boy = 0.8
    Mass of plank = 40kg Distance to C.O.M = 1.2

    46g * 0.8 = 40g * 1.2 + C
    313.6 = 361 + C
    C is negative so the boy can stand.

    That's how I did it.
    Offline

    3
    ReputationRep:
    (Original post by mbh16)
    oh right ok so how did u draw the graph?, cause it said that u could use the graph to explain
    It said you can draw ON the graph, not draw a graph haha. So I drew a dotted line between when the gradient is increasing and when the gradient is 0. Then labelled resistive force=driving force and resistive force < driving force. Hope I'm right
    Offline

    0
    ReputationRep:
    (Original post by philo-jitsu)
    What were the other questions for the velocity one...

    It was 5ms up and sin25....rearrange to get 11.83

    Then i think one question was how high it travvelled which was done using suvat and i got 1.27m up or 1.3m rounded.

    Another was horizontal distance travveled which was done by pythagorus of 11.83^2 -5^2 and sqroot to find horizontal speed....then times by flight time of 1.3s which gets s=13.9m

    The diamonds ones i sped through so need help remembering....the second material had a higher refractive index...bare with
    Considering a human is 1.8mish I think it would be higher than that, but I'm probably just saying that to make me convinced my 13m answer was right.
    Offline

    2
    ReputationRep:
    (Original post by TSRPAV)
    swear the boy can stand on it? if you take moments about the end of the plank(one not on embankment) and do at a point of tilting around the rock senario the wieght of the plank and its distance from rock is grater than the wieght of the boy and his distance from rock so he can
    Took moments about the rock to find out the maximum mass that can be put on before tilting (when reaction at the bank = 0)

    That mass was 48kg

    46<48 therefore he can stand without tilting
 
 
 
Poll
Do you agree with the PM's proposal to cut tuition fees for some courses?

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Write a reply...
Reply
Hide
Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.