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Math Mechanics 9709 November 2017 Paper 42

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chichibung

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First of all, 24 hours have passed since the exam so i'm guessing we are able to discuss anything about the exam.
Anybody remember the question where we had to find the value of time for which both particles of P and Q were traveling in the same direction? How did you do it, and what was the answer?
Also any guesses on the grade boundaries?
 
MahiTheKilla

MahiTheKilla

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0.2 seconds upwards, 0.4 seconds downwards. So total 0.6s travelled in the same direction. I might be wrong tho..
 
MahiTheKilla

MahiTheKilla

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I took an extra paper, drew the whole diagram and pictured the system in my mind. I dont know how to explain it :p Just used the simple kinematics formulas. First of all, the question stated that Q was thrown 1 second later, 5m above of P.

So first, I calculated the maximum vertical distance travelled by both the particles and their relative time. P travelled upwards for 1.2s, and downwards for 1.2s. Q travelled upwards for 1s. However, Q was thrown 1 second after P, so they have an interval of 0.2s of travelling upwards together, until P reaches its maximum height and starts travelling downwards for another 1.2s

Now 0.2 seconds have passed, Q is going to travel upwards for another 0.8s while P moves downwards. After 0.8s, Q finally starts to move downwards, but as P will travel for 1.2s, only 0.4s remain. So they both then travel. 0.4s downwards.

One more thing also to note, the question never mentioned whether Q was going to fall back to it's original ground 5m above the relative ground of P. So I just assumed both particles fell on the ground of P. In that sense, Q travels 5m upwards and 10m DOWNWARDS. Although I think this issue is neglegible as for both cases, they would travel downwards for 0.4s anyways :p haha.
 
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chichibung

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I remember clearly the question saying "Find the values of t..." which im guessing we had to find an inequality, but because the particle would go up and then down, we would have to find 2 inequality equations. But i believe the question said "if t was the time P was moving and q was released at t=1..."(or something like that) in the end, i wrote the answer as 1<t<1.2 and 2<t<2.4. Would really appreciate it if anybody could say if my answer would atleast be considered correct
by the way, the question looked something like this:

Particle P is released vertically from horizontal ground with a speed of 12ms^-1. If T was the time for particle P, and particle Q was released vertically with speed of 10ms^-1 at T=1, particle Q was released 5 meters above the horizontal ground. Find the values of T for which both particles are moving in the same directions.

The question did not indicate if we should take into account when they travel downwards however im guessing we had to. The question was 4 marks
 
MahiTheKilla

MahiTheKilla

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First and foremost, as far as I recall the question said find the total time the two particles move in the same direction. But its no biggie, I have a friend who gave the answer in inequalities just like you and he got 46/50 in M1 back in May/June (he's repeating). And yeah the question was designed to confuse students. Every year a question like this comes which distinguishes between the top students. Dont worry too much though you got half of the answer right, you will get marks. And yes ofcourse you have to take both directions into consideration, the question was of 4 marks I believe and this was the technical part of it.
 
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MahiTheKilla

MahiTheKilla

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By the way that friend of mine had the same answer as mine just in two inequalities.
 
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sivanthi

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Um I got those two answers but I put 1less than or equal to t<1.2 for the first inequality because I thought that they are moving in the same direction at t=1 itself. Do you guys remember what your m was for the pulley question. I got m=5. And also for the very last displacement calculation did you integrate v between the limits 2 and 20 or what. And also does anyone remember getting a velocity of 6.68 for the plonk power question? I really hope the thresholds are low
 
Dukula Jayasinghe

Dukula Jayasinghe

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The answer should be an inequality. No other answers are accepted it seems. They say find values of 'T'
 
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sivanthi

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MahiTheKilla said:
First and foremost, as far as I recall the question said find the total time the two particles move in the same direction. But its no biggie, I have a friend who gave the answer in inequalities just like you and he got 46/50 in M1 back in May/June (he's repeating). And yeah the question was designed to confuse students. Every year a question like this comes which distinguishes between the top students. Dont worry too much though you got half of the answer right, you will get marks. And yes ofcourse you have to take both directions into consideration, the question was of 4 marks I believe and this was the technical part of it.
Click to expand...
I’m sorry but I pretty sure the question said give the set of values which means inequality
 
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sivanthi

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I think the thresholds will be high this year because everyone in our school found it ok. And did you use exact values for sin and cos to calculate m?
 
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