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help? horrible physics questions
Right. Two horrible physics questions from a non-physicist:
1. Radioactive Polonium 214 can decay into Polonium 210 by emitting an alpha particle followed by...
C) Two negative beta particles
^ This is the correct, official answer but I am confused as to why this is the case. I've worked it out to be two postive beta particles.
2. A small object of mass m is suspended from a fixed point O by a light, inextensible cord. The object is raised until the cord is horizontal and then released. It moves in an arc of a circle as shown in
The answer is 3mg.
But I have no idea why! Can someone help me please?
1. Radioactive Polonium 214 can decay into Polonium 210 by emitting an alpha particle followed by...
C) Two negative beta particles
^ This is the correct, official answer but I am confused as to why this is the case. I've worked it out to be two postive beta particles.
2. A small object of mass m is suspended from a fixed point O by a light, inextensible cord. The object is raised until the cord is horizontal and then released. It moves in an arc of a circle as shown in
The answer is 3mg.
But I have no idea why! Can someone help me please?
natsy
Right. Two horrible physics questions from a non-physicist:
1. Radioactive Polonium 214 can decay into Polonium 210 by emitting an alpha particle followed by...
C) Two negative beta particles
^ This is the correct, official answer but I am confused as to why this is the case. I've worked it out to be two postive beta particles.
2. A small object of mass m is suspended from a fixed point O by a light, inextensible cord. The object is raised until the cord is horizontal and then released. It moves in an arc of a circle as shown in
The answer is 3mg.
But I have no idea why! Can someone help me please?
1. Radioactive Polonium 214 can decay into Polonium 210 by emitting an alpha particle followed by...
C) Two negative beta particles
^ This is the correct, official answer but I am confused as to why this is the case. I've worked it out to be two postive beta particles.
2. A small object of mass m is suspended from a fixed point O by a light, inextensible cord. The object is raised until the cord is horizontal and then released. It moves in an arc of a circle as shown in
The answer is 3mg.
But I have no idea why! Can someone help me please?
you need to conserve charge.
Po-214 --> Po-10 + a(2+) + 2e(-)
you have to conserve charge so it has to be a negatively charged beta particle. Another way to look at it is that an alpha particle consists of 2 protons and 2 neutrons, if you lose 2 protons your element will change to one with Z-2 protons. To get back to polonium you need to convert 2 neutrons into protons, which if memory serves correct requires negative beta particles to be produced.
As for the second bit, what are you even trying to find? I don't see that it says it anywhere.
Silly me. I was tired and forgot to write the actual 'question' part of the question...
A small object of mass m is suspended from a fixed pt O by a light, inextensible circle as shown in the figure (see above link).
When it passes through it's lowest position at point P, the tension in the cord is...
A small object of mass m is suspended from a fixed pt O by a light, inextensible circle as shown in the figure (see above link).
When it passes through it's lowest position at point P, the tension in the cord is...
Also - thank you for explaining the radioactivity question. It makes perfect sense now.
No that's it:
A small object of mass m is suspended from a fixed pt O by a light, inextensible cord. THe object is raised until the cord is horizontal and then released. It moves in an arc of a circle as shown above in the attachment.
When it passes through its lowest position at pt P, the tension in the cord is...
1) zero
2) mg
3) 2mg
4) 3mg
A small object of mass m is suspended from a fixed pt O by a light, inextensible cord. THe object is raised until the cord is horizontal and then released. It moves in an arc of a circle as shown above in the attachment.
When it passes through its lowest position at pt P, the tension in the cord is...
1) zero
2) mg
3) 2mg
4) 3mg
OK, got it.
The tension at the bottom is the weight PLUS the centripetal force, I just couldn't see how to get the centripetal force.
Use energy conversion - potential to kinetic - from the point where the cord is horizontal (all potential) to the lowest point (all kinetic)
mgr = 0.5 mv^2
Rearrange
2mg = m v^2 / r
And mv^2 / r is the centripetal force, therefore the force is 2mg.
Add it to the weight and there's the Tension.
The tension at the bottom is the weight PLUS the centripetal force, I just couldn't see how to get the centripetal force.
Use energy conversion - potential to kinetic - from the point where the cord is horizontal (all potential) to the lowest point (all kinetic)
mgr = 0.5 mv^2
Rearrange
2mg = m v^2 / r
And mv^2 / r is the centripetal force, therefore the force is 2mg.
Add it to the weight and there's the Tension.
Right. I see.
That's very clever - thank you for explaining.
(ps. I would rep you for being so helpful, but a) i don't really know how to b) i don't think my rep is worth anything at the moment. But the thought def. is there!
That's very clever - thank you for explaining.
(ps. I would rep you for being so helpful, but a) i don't really know how to b) i don't think my rep is worth anything at the moment. But the thought def. is there!
natsy
Right. I see.
That's very clever - thank you for explaining.
(ps. I would rep you for being so helpful, but a) i don't really know how to b) i don't think my rep is worth anything at the moment. But the thought def. is there!
That's very clever - thank you for explaining.
(ps. I would rep you for being so helpful, but a) i don't really know how to b) i don't think my rep is worth anything at the moment. But the thought def. is there!
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