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# M2 help Watch

1. Need some help with 5i.

Not entirely sure. I tried first saying the speed it hits the ground is v^2=u^2+2as.
U=5 so v^2=2as v^2=5^2+2×9.8×1.4. Which gave me v= 7.507
Im not sure on the coefficent of resitution bit.
Is it 0.7= 7.507/ speed the ball comes back or the other way round?

Also what is the com of a semi circle?
http://m.imgur.com/A11mEmK
2. (Original post by Super199)
Need some help with 5i.

Not entirely sure. I tried first saying the speed it hits the ground is v^2=u^2+2as.
U=5 so v^2=2as v^2=5^2+2×9.8×1.4. Which gave me v= 7.507
Im not sure on the coefficent of resitution bit.
Is it 0.7= 7.507/ speed the ball comes back or the other way round?

Also what is the com of a semi circle?
http://m.imgur.com/A11mEmK

Otherway around it should be speed the ball comes back up = 0.7 * 7.507.

COM of a semi circle is along its radius from the diameter.
3. (Original post by Zacken)
Otherway around it should be speed the ball comes back up = 0.7 * 7.507.

COM of a semi circle is along its radius from the diameter.
Sound. How did you get the com of a semi circle that?
4. (Original post by Super199)
Sound. How did you get the com of a semi circle that?
Should be in your formula booklet for "sector of circle" with the angle as , just set and you're good to go.
5. (Original post by Super199)
Sound. How did you get the com of a semi circle that?
Formula book for m2, it is proved in m3 i believe and involves some integration but you can almost certainly quote it as a standard result for your purposes

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