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# i Need help for isaacphysics assignment please!!!!! ASAP!

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1. 1) A current of 5.5mA5.5mA is flowing through a resistance of 220kΩ Find the potential difference (in volts) across the resistance.

5.5 mA =5,500,000 A , 220 kohms =220,000 ohms. P.D= IxV, = 5,500,000 X 220,000 = 1.21 X 10^12 Volts
i got : 1.21x10^12. but it says sig figs are incorrect? WHERE have i gone wrong???
2. (Original post by poonshark)
1) A current of 5.5mA5.5mA is flowing through a resistance of 220kΩ Find the potential difference (in volts) across the resistance.

5.5 mA =5,500,000 A , 220 kohms =220,000 ohms. P.D= IxV, = 5,500,000 X 220,000 = 1.21 X 10^12 Volts
i got : 1.21x10^12. but it says sig figs are incorrect? WHERE have i gone wrong???
Hello there,

Firstly, if you have transcribed the problem correctly, then represents ; the correct way to read is 'milli-amperes'. If you instead meant to type , then your interpretation would be correct.Your interpretation of the resistance is correct and you can now use Ohm's law, to calculate the potential difference.

(2 significant figures)

I think Isaac Physics wants you to quote your answer to two significant figures, as this is the minimum number of significant figures that have been given to you in the question.

I hope that this has been helpful.

Smithenator5000.
3. (Original post by Smithenator5000)
Hello there,

Firstly, if you have transcribed the problem correctly, then represents ; the correct way to read is 'milli-amperes'. If you instead meant to type , then your interpretation would be correct.Your interpretation of the resistance is correct and you can now use Ohm's law, to calculate the potential difference.

(2 significant figures)

I think Isaac Physics wants you to quote your answer to two significant figures, as this is the minimum number of significant figures that have been given to you in the question.

I hope that this has been helpful.

Smithenator5000.
Thank you, that helps a lot! I didn't realise the unit was milli-amperes
4. (Original post by poonshark)
Thank you, that helps a lot! I didn't realise the unit was milli-amperes
You're very welcome All the best with the assignment.
5. (Original post by Smithenator5000)
You're very welcome All the best with the assignment.
Sorry to bother you but there is a question on my assignment which i have never been taught, i am a bit confused how it works?

I am given this table-

and these questions -

Attached Images

6. (Original post by poonshark)
Sorry to bother you but there is a question on my assignment which i have never been taught, i am a bit confused how it works?

I am given this table-

and these questions -

Hello there,

I am surprised that you haven't been taught this; it is pretty important. For the first part, it wants you to be able to write the units on the left in an equivalent form. All of these units can be expressed in terms of the seven 'base units'. These are:

source:http://physics.nist.gov/cuu/Units/units.html

You can find the base unit representations by using a formula that you know and treating the units like variables. For example, the Newton is a unit of force. One equation involving force is , a form of Newton's Second Law. This equation implies that , where represents the units of quantity . We can use this to find the base unit representation of the Newton.

You would enter this into Isaac Physics by telling it the power of each unit it lists.

Smithenator5000.
7. (Original post by Smithenator5000)
Hello there,

I am surprised that you haven't been taught this; it is pretty important. For the first part, it wants you to be able to write the units on the left in an equivalent form. All of these units can be expressed in terms of the seven 'base units'. These are:

source:http://physics.nist.gov/cuu/Units/units.html

You can find the base unit representations by using a formula that you know and treating the units like variables. For example, the Newton is a unit of force. One equation involving force is , a form of Newton's Second Law. This equation implies that , where represents the units of quantity . We can use this to find the base unit representation of the Newton.

You would enter this into Isaac Physics by telling it the power of each unit it lists.

Smithenator5000.
Thanks again! I'll give this a go.
8. (Original post by poonshark)
Thanks again! I'll give this a go.
You're welcome. Do not hesitate to ask for help if required.
9. (Original post by Smithenator5000)
You're welcome. Do not hesitate to ask for help if required.
Hi , i have to find the area under the line in the graph. I don't understand where i gone wrong? i got (25x5)/2 + 25x1 = 87.5 - 88 to 2 sf. This is the graph i have.
10. (Original post by poonshark)
Hi , i have to find the area under the line in the graph. I don't understand where i gone wrong? i got (25x5)/2 + 25x1 = 87.5 - 88 to 2 sf. This is the graph i have.
Hello there,

Notice that the y-axis (showing current in amperes) starts from , as opposed to . I believe that the question wants you to consider the area which includes that which has been omitted from the graph. Here is a diagram of what I am trying to describe.

You can now try calculating the area of this. Please reply if this doesn't work.

Smithenator5000.
11. (Original post by Smithenator5000)
Hello there,

Notice that the y-axis (showing current in amperes) starts from , as opposed to . I believe that the question wants you to consider the area which includes that which has been omitted from the graph. Here is a diagram of what I am trying to describe.

You can now try calculating the area of this. Please reply if this doesn't work.

Smithenator5000.
Of course! i understand now. Thanks i wouldn't have realised that. Are you a physics teacher or something?
12. (Original post by poonshark)
Of course! i understand now. Thanks i wouldn't have realised that. Are you a physics teacher or something?
You are very welcome. It is always worth checking for things like that. Personally, I think they should have indicated the transposed scale with a scribble on the y-axis like so:

source: http://www2.ccsd.ws/sbfaculty/team8e...g%20Points.htm

I am actually an upper sixth student at the moment, so I have just completed my AS in physics and am now studying for full A-levels in physics, maths and further maths. Where are you at?
13. (Original post by Smithenator5000)
You are very welcome. It is always worth checking for things like that. Personally, I think they should have indicated the transposed scale with a scribble on the y-axis like so:

source: [/b]

I am actually an upper sixth student at the moment, so I have just completed my AS in physics and am now studying for full A-levels in physics, maths and further maths. Where are you at?
i have just started AS level. i was assigned loads physics homework on isaac physics which is due in on monday. I am studying maths ,physics, economics , and chemistry for AS.

Also how would you go about calculating the area under these two non-linear graphs? I tried to estimate them but i failed

14. (Original post by poonshark)
i have just started AS level. i was assigned loads physics homework on isaac physics which is due in on monday. I am studying maths ,physics, economics , and chemistry for AS.
Cool. Are you enjoying it so far? I suppose that the physics homework is supposed to be a prerequisite task. Otherwise I find it strange that your teacher assigned it to you, given that you claim that they haven't taught you some of it.
15. (Original post by Smithenator5000)
Cool. Are you enjoying it so far? I suppose that the physics homework is supposed to be a prerequisite task. Otherwise I find it strange that your teacher assigned it to you, given that you claim that they haven't taught you some of it.
Yeah we have't been given any lessons yet at all, but we need to have these assignements completed by the first lesson on monday. also how would you go about calculating the area under these non linear graphs? i tried to estimate them but i failed

16. (Original post by poonshark)
Yeah we have't been given any lessons yet at all, but we need to have these assignements completed by the first lesson on monday. also how would you go about calculating the area under these non linear graphs? i tried to estimate them but i failed

It depends on what information you have about them. The first one could be estimated by calculating the combined area of a trapezium (up to ) and a rectangle (from and onward). For the second and third one, exact areas can be calculated by integration (though I expect that you won't have learned about that yet). To do this however, you need to know the exact equations of the lines and besides, A-level physics does not expect this knowledge. The traditional way to estimate the areas is by splitting the area up into trapeziums and summing their areas. For each of these graphs, you should be cautious, as the some of the units have prefixes. If you have already tried this, could you post your calculations?
17. (Original post by Smithenator5000)
It depends on what information you have about them. The first one could be estimated by calculating the combined area of a trapezium (up to ) and a rectangle (from and onward). For the second and third one, exact areas can be calculated by integration (though I expect that you won't have learned about that yet). To do this however, you need to know the exact equations of the lines and besides, A-level physics does not expect this knowledge. The traditional way to estimate the areas is by splitting the area up into trapeziums and summing their areas. For each of these graphs, you should be cautious, as the some of the units have prefixes. If you have already tried this, could you post your calculations?
so because some have prefixes, would you have to convert the values back into standard units before calculating e.g convert uS into seconds ?
18. (Original post by poonshark)
so because some have prefixes, would you have to convert the values back into standard units before calculating e.g convert uS into seconds ?
Yes, I would advise converting the values to standard units before using them in your calculations.
19. (Original post by poonshark)
so because some have prefixes, would you have to convert the values back into standard units before calculating e.g convert uS into seconds ?
here is the graphs again in a more complete view , no extra infomation has been given

20. (Original post by poonshark)
here is the graphs again in a more complete view , no extra infomation has been given

This is okay. You should now split the areas into trapeziums like this:

You can then calculate the area of each trapezium and add them together to get the total area. You can make the estimate more accurate by increasing the number of trapeziums.

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