Edexcel Mathematics: Mechanics M3 6679 01 - 17 May 2017 [Exam Discussion]

Wait, it's not 1/5???

That's right.

MS

1. 3/4
2. theta = 33.6 (degrees) l = 0.2m
3. (a) 4.52ms^-1 (b) 5.42m
4. (a) 25/11a (b) theta =23.7 (degrees)
5. (b) 5mg>mg (c) v(max) = 3sqrt(ga)
6. (b) F=38.4N (c) v=6.5ms^-1
7. (a) AO =2.2m (b) a = -625/9x (c) T=1.02 seconds

model anwsers

https://www.thestudentroom.co.uk/showthread.php?t=4718256&p=71502464#post71502464

For question 6c, why was the change in gravitational potential energy not calculated? I calculated the GPE during the exam, now I'm worried I made a silly mistake.

the table was turned sideways in a way, causing the force of weight to act perpendicular, no change in gpe occured. I wuldnt stressed too much as i dont see how u could be penalised more than 3 marks for this

the table was turned sideways in a way, causing the force of weight to act perpendicular, no change in gpe occured. I wuldnt stressed too much as i dont see how u could be penalised more than 3 marks for this

For question 5b (the vertical motion question where you had to 'verify' that the particle moves in a complete circle). I did something different to what they wanted I think, would appreciate it if anyone could tell if I'm wrong on this one.

So yeah I wasn't sure what to do so I resolved towards the center and got an equation of the normal reaction $R$ on the particle:

$R=mg(7+3sin\theta)$

I then said that since $-1\leqslant sin\theta \leqslant1$ then $4mg\leqslant R \leqslant10mg$ so $R>0$ for all values of $\theta$.

I then showed that the speed $v$ at the top when $\theta=270^{\circ}$ was greater than zero.

So $R>0$ for all $\theta$ and $V>0$ at top of circle is what I showed. Would this be enough to verify that the particle moves in a complete circle? Or I have not really done what they asked?

Yeah. You find the smallest value of v^2. Then if R>0 for this value, the particle stays in contact.
It was 7+ 2sin (theta) though, not 3.

Found it easier than last year but last year's boundaries were 72 and 69...

How many marks was the question 6? (I messed up and thought it was vertical 😭😭)