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# mechanics question watch

1. hey could anyone help me with this mechanics question, i have attached the scan of it. its jus part a i need help with, i keep gettin the thrust to be zero somehow! thanks
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3. I'll give it a go...
First a bit of trig to find the size of angle alpha:
Right angled triangle so we get tan(alpha)=o/a=1/2.4 gives alpha=22.6°(3 s.f.).
Then moments take about the bottom of the display board (the bit touching the ground)
clockwise moments = anticlockwise moments
1.5m x component of weight of board = 2.4m x thrust
1.5 x 26cos(alpha) = 2.4 x thrust
thrust = (1.5 x 26cos(alpha))/2.4
thrust = 15N
4. the book says 1.5 but i guess thats jus an error in decimal point doh, seein as u got the same as me on my third attempt! thanks
5. hmm, I'm not sure.
6. i got 15N as well
7. If it's from one of those aim higher books, perhaps could be a reason.
8. oh wow how did u know?! yeah it is from that book, are most of the answers wrong then?!
9. We use the M1 one, and it does have quite a lot of wrong answers in it.
10. yeah i have noticed quite a lot of wrong answers in the M3 one...it's not good, thanks for the help tho.
11. I got 15N!
12. 15n

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