Lower Secondary Science

[Vivian22]

Dr.Daniel:

Concerning statement (2) only,


For the portion of the wire moved in the same direction as the magnetic field there will be no induced current. Only portions of the wire that have a component of the magnetic field perpendicular to the motion of the wire will have induced current. I'll try to describe 3 dimensions. Imagine a 3-D system of x being horizontal, y being vertical and z being in and out of the page. So the portion of the wire at y=0 is being pushed parallel to the magnetic field, along the z axis, meaning right along the magnetic field lines. That has no induced current. If you can see that much, then this is probably enough to get to the right answer in the problem.

If you start to think that points on the wire above and below the magnet many not be exactly parallel to the magnetic field, then what I am saying is whatever induction occurs below the plane of the magnet is opposite in direction to whatever induction occurs above the plane of the magnet.

Oh I get it now. Thank you!

[Vivian22]

Hi,


Can someone now help me with this Chemistry question? How do we derive at the answer? Thanks in advance! http://i44.tinypic.com/35n4py8.png\">

[Dr.033430Daniel]

Vivian22:

Hi,


Can someone now help me with this Chemistry question? How do we derive at the answer? Thanks in advance! http://i44.tinypic.com/35n4py8.png\">

The winner is B. Nitrogen needs three more electrons to form a complete outer shell and I see that symbol Q has three lines coming from it. Each one of those lines represents a bond or shared electron. Symbol R has 4 lines connected to it, meaning it has four bonds. Elements that do that are in the Carbon, Silicon group (vertical column) , so R could be Silicon. And symbol V has a single bond, so it could be Hydrogen, which needs one more electron to complete the valence shell.

Choice A is no good because there is no way Q is Fl. Fl just needs one bond to get to the noble gas (full valence shell) configuration. Also there is no way V is Si because it is only forming one bond. Si will form 4.

Choice C is no good because Q is not Oxygen. Oxygen will have two bonds for two shared electrons.

And D is no good because Q is not Si for reasons stated above.

I just received a neat chemistry model kit and sometimes have students put together some molecules in class. Its great because each element has a different color and there are a certain number of holes drilled in wooden spheres so that you know how many bonds each element makes. You connect the wooden spheres with little wooden rods. Also the holes are drilled at the correct bond angles so that you can see the proper shape of each molecule.

[Vivian22]

Dr.Daniel:

Vivian22:

Hi,


Can someone now help me with this Chemistry question? How do we derive at the answer? Thanks in advance! http://i44.tinypic.com/35n4py8.png\">

The winner is B. Nitrogen needs three more electrons to form a complete outer shell and I see that symbol Q has three lines coming from it. Each one of those lines represents a bond or shared electron. Symbol R has 4 lines connected to it, meaning it has four bonds. Elements that do that are in the Carbon, Silicon group (vertical column) , so R could be Silicon. And symbol V has a single bond, so it could be Hydrogen, which needs one more electron to complete the valence shell.

Choice A is no good because there is no way Q is Fl. Fl just needs one bond to get to the noble gas (full valence shell) configuration. Also there is no way V is Si because it is only forming one bond. Si will form 4.

Choice C is no good because Q is not Oxygen. Oxygen will have two bonds for two shared electrons.

And D is no good because Q is not Si for reasons stated above.

I just received a neat chemistry model kit and sometimes have students put together some molecules in class. Its great because each element has a different color and there are a certain number of holes drilled in wooden spheres so that you know how many bonds each element makes. You connect the wooden spheres with little wooden rods. Also the holes are drilled at the correct bond angles so that you can see the proper shape of each molecule.

Thank you! That was a great explanation :goodpost:

[fruittypie]

excellent! Thanks for sharing

[fruittypie]

Vivian22:

Dr.Daniel:

[quote=\"Vivian22\"]Hi,


Can someone now help me with this Chemistry question? How do we derive at the answer? Thanks in advance! http://i44.tinypic.com/35n4py8.png\">

The winner is B. Nitrogen needs three more electrons to form a complete outer shell and I see that symbol Q has three lines coming from it. Each one of those lines represents a bond or shared electron. Symbol R has 4 lines connected to it, meaning it has four bonds. Elements that do that are in the Carbon, Silicon group (vertical column) , so R could be Silicon. And symbol V has a single bond, so it could be Hydrogen, which needs one more electron to complete the valence shell.

Choice A is no good because there is no way Q is Fl. Fl just needs one bond to get to the noble gas (full valence shell) configuration. Also there is no way V is Si because it is only forming one bond. Si will form 4.

Choice C is no good because Q is not Oxygen. Oxygen will have two bonds for two shared electrons.

And D is no good because Q is not Si for reasons stated above.

I just received a neat chemistry model kit and sometimes have students put together some molecules in class. Its great because each element has a different color and there are a certain number of holes drilled in wooden spheres so that you know how many bonds each element makes. You connect the wooden spheres with little wooden rods. Also the holes are drilled at the correct bond angles so that you can see the proper shape of each molecule.

Thank you! That was a great explanation :goodpost:[/quote]Are you a student? Do you mind to email the papers to me?

Thanks

[kitty2]

Dr Daniel,can you help with these questions? :thankyou:


A block of wood is brought to the planet Mars.
1) state if there will be a change in mass and explain why?
2)state if there will be a change in weight and explain why?
3) find the weight,given that mass is 500g.

[Dr.033430Daniel]

kitty2:

Dr Daniel,can you help with these questions? :thankyou:


.

A block of wood is brought to the planet Mars.
1) state if there will be a change in mass and explain why?

There is no change in mass. Mass is the amount of matter in a substance. It is how much material is present. So no matter where you are: on Earth, the Moon, Mars, even in space far away from any planet or star, you always have mass. 500 grams is always 500 grams.

2)state if there will be a change in weight and explain why?

Weight in physics refers to the force of gravity acting on a mass. Weight is expressed in the SI units of Newtons. On the earth, the gravitational field strength is 10N/kg (the value used in secondary schools preparing for the O-Level), meaning every 1kg has a force of 10N acting on it. On mars, the gravitational field strength is less, only 3.7 N/kg. So that means that on Mars, you can have the same amount of mass, but it weighs less.

3) find the weight,given that mass is 500g.

You take the mass in kg times the gravitational field strength on Mars. The mass is 0.5kg and the gravitational field strength on Mars is 3.7N/kg, so multiplying those together you get a weight of 1.85N.

I always tell the students that it is possible that someone sitting in school today may walk on Mars. I hope the USA gets off their butts and takes the lead on this, but if they do not, someone else will. And the trip to Mars will need scientists of all kinds. Engineers to build the space ship, chemists to help the astronauts breathe on the way there, biologists to help grow plants on Martian soil, the list goes on. My Father played a small part in the Apollo moon landing project by designing a pressure gage that is sitting on the moon right now, so I always try to inspire students to think about the potential of a manned mission to mars.

[kitty2]

Dr.Daniel:

kitty2:

Dr Daniel,can you help with these questions? :thankyou:


.

A block of wood is brought to the planet Mars.
1) state if there will be a change in mass and explain why?

There is no change in mass. Mass is the amount of matter in a substance. It is how much material is present. So no matter where you are: on Earth, the Moon, Mars, even in space far away from any planet or star, you always have mass. 500 grams is always 500 grams.

2)state if there will be a change in weight and explain why?

Weight in physics refers to the force of gravity acting on a mass. Weight is expressed in the SI units of Newtons. On the earth, the gravitational field strength is 10N/kg (the value used in secondary schools preparing for the O-Level), meaning every 1kg has a force of 10N acting on it. On mars, the gravitational field strength is less, only 3.7 N/kg. So that means that on Mars, you can have the same amount of mass, but it weighs less.

3) find the weight,given that mass is 500g.

You take the mass in kg times the gravitational field strength on Mars. The mass is 0.5kg and the gravitational field strength on Mars is 3.7N/kg, so multiplying those together you get a weight of 1.85N.

I always tell the students that it is possible that someone sitting in school today may walk on Mars. I hope the USA gets off their butts and takes the lead on this, but if they do not, someone else will. And the trip to Mars will need scientists of all kinds. Engineers to build the space ship, chemists to help the astronauts breathe on the way there, biologists to help grow plants on Martian soil, the list goes on. My Father played a small part in the Apollo moon landing project by designing a pressure gage that is sitting on the moon right now, so I always try to inspire students to think about the potential of a manned mission to mars.

:thankyou: Dr Daniel :salute:

[Crester]

Hi, need help in this Physics Ques.

1)a small cork is fixed with wax to a metal plate. An electric heater is placed close to thè plate. After some time, the wax melts and the cork drops off.
How does the heat reach the wax?
A) by conduction only
B) by conduction and convection
C) Radiation and conduction
D) Radiation and convection

Thanks.