![]() ![]() The main difference is that gravitational forces are always attractive, while electrostatic forces can be attractive or repulsive. The force equations are similar, so the behavior of interacting masses is similar to that of interacting charges, and similar analysis methods can be used. ![]() The gravitational force between two masses (m and M) separated by a distance r is given by Newton's law of universal gravitation:Ī similar equation applies to the force between two charges (q and Q) separated by a distance r: If you understand gravity you can understand electric forces and fields because the equations that govern both have the same form. It's more accurate to call g the gravitational field produced by the Earth at the surface of the Earth. When talking about gravity, we got into the (probably bad) habit of calling g "the acceleration due to gravity". We've talked about gravity, and we've even used a gravitational field we just didn't call it a field. The fact is, though, that you're already familiar with a field. Many people have trouble with the concept of a field, though, because it's something that's hard to get a real feel for. It's a powerful concept, because it allows you to determine ahead of time how a charge will be affected if it is brought into the region. The parallel between gravity and electrostaticsĪn electric field describes how an electric charge affects the region around it. Example 16-4 in the textbook shows this process. ![]() If it wasn't so symmetric, all you'd have to do is split the vectors up in to x and y components, add them to find the x and y components of the net force, and then calculate the magnitude and direction of the net force from the components. The symmetry here makes things a little easier. When this is combined with the 64.7 N force in the opposite direction, the result is a net force of 118 N pointing along the diagonal of the square. In this problem we can take advantage of the symmetry, and combine the forces from charges 2 and 4 into a force along the diagonal (opposite to the force from charge 3) of magnitude 183.1 N. You have to be very careful to add these forces as vectors to get the net force. If you have the arrows giving you the direction on your diagram, you can just drop any signs that come out of the equation for Coulomb's law.Ĭonsider the forces exerted on the charge in the top right by the other three: Force is a vector, and any time you have a minus sign associated with a vector all it does is tell you about the direction of the vector. You should also let your diagram handle your signs for you. To solve any problem like this, the simplest thing to do is to draw a good diagram showing the forces acting on the charge. What is the net force exerted on the charge in the top right corner by the other three charges? The charges in the other two corners are -3.0 x 10 -6 C. The two charges in the top right and bottom left corners are +3.0 x 10 -6 C. Remember, too, that charges of the same sign exert repulsive forces on one another, while charges of opposite sign attract.įour charges are arranged in a square with sides of length 2.5 cm. Remember that force is a vector, so when more than one charge exerts a force on another charge, the net force on that charge is the vector sum of the individual forces. The force exerted by one charge q on another charge Q is given by Coulomb's law: ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |