# Search results

1. ### Dimensionally correct equations

when you work with dimensions, use the fundamental units. mass : kilogram: [kg] length : meter : [m] time : second : [s] so speed ; [m]/[s] acceleration : [m]/[s]^2 force in newtons [N] = [kg][m]/[s]^2 work or energy is in joules [J] = [N][m] = [kg][m]^2 /[s]^2 When you have a formula, it...
2. ### Gravitation Constant

The gravitationnal constant is realy 6.67x10^-11 Nm^2/kg^2
3. ### Gravitation Constant

Hello everybody, gravitationnal acceleration is g = 9.8 m/s^2. It is when you analyse a situation let's say that an object is moving upward, you know that its weight is downward, so when you have a situation in which there are two opposite directions, you choose one that is positive (usually the...
4. ### Electric field with three charges

a test charge halfway between q2 and q3,call this point M, will experience a repulsion from q2, attraction from q3 with the same intensity. so the electric field at M will have a component along the line joining M and q3. But the same test charge at M will also experience a repulsion from q1...
5. ### Electric field with three charges

Hi flipstyle, you have an equilateral triangle, so if you trace a line which joint q3 and the midpoint between q1 q2, the lengh of this segment will be d√3/2. A test charge placed at halfway between q1 and q2 will be affected only by q3 since the influence of q1 and q2 cancel each other. So the...
6. ### Dalton's Law

When you heath water, the water pressure augment at the interface between water and air The boiling point of water vary with the pressure of the atmosphere. At sea level the boiling point is 100 ˚C where the air pressure is highest. At higher altitude the pressure of the atmosphere is getting...
7. ### Net force on charges found to be zero

I eltel, you must analyse two cases: A negative then B must be positive so that the net force be zero on p. A positive then B must be negative.... Then use Coulomb's law to complete your reasoning.
8. ### Derivative of inverse hyperbolic trigonometric functions

there is an error in the calculations of SatusX. The basic relation with hyperbolic function is cosh^2 x - sinh^2 x = 1. Now if y = sinh-1 x than x = sinh y dx/dy = coshy but cosh^2 y = 1+sinh^2y =1+x^2. so dy/dx =1/sqrt(1+x^2) where sqrt means square root. bye
9. ### How much total kinetic energy is needed in this case?

Hi eri3an, you must remember Einstein's equation : E = mc^2, where m is the mass of the particle when it is moving.
10. ### Problems with relativity

You have to remember the famous equation of Einstein: E = mc^2. Where m is the mass of the particle when it moves. the kinetic energie is the difference between the energy of the particle when it is movin and the rest energy (the energy that the particle has when it is at rest). You must know...
11. ### Qns on potential energy and forces

The potential energy is positive. So there is an attraction toward the origin. The force = - (dW/dx) = -2kx. So the force is directed from the point P to the point O, the origin. bye
12. ### Production of electric current

Suppose that the magnetic field is vertical upward. Suppose you have a round loop in a horizontal plane. Now rotate the loop along an axis wich is horizontal. What will happen to the flux of the magnetic field through the loop?
13. ### Does a current produce an electric field?

A current in a wire can be viewed as the two types of charges moving in opposite direction. Say in a horizontal wire, from left to right, negative charges moving to the left and positive charges moving to the right. So for a test test charge at rest outside the wire, the wire will be neutral...
14. ### Circuit that is both parallel and in series

I have juste made the calculations and I arrived at 0.98 watt ? 1 watt. So the result of sdekivit seems ok
15. ### Circuit that is both parallel and in series

I have juste made the calculations and I arrived at 0.98 watt ≈ 1 watt. So the result of sdekivit seems ok
16. ### Acceleration Word Problem

Remember, think physics first, whenever you are new to physics Don't just play with formulas. Use basic concepts. Know how to calculate distance. The only few thing you must realy know is this distance = mean velocity * time acceleration = (final velocity- initial velocity)/(time it takes to...
17. ### Acceleration Word Problem

When the acceleration is constant, remember these equations: <v> = (vf +vi)/2 = mean velocity. If t = time required to stop, distance required to stop = d = <v>t vf = final velocity vi = initial velocity Now y ou must remember the definition of acceleration acceleration = a= (? - ?)/...
18. ### Calculating Electric Field Magnitude and Direction

The calculations for the intensity of the electric field made by Kaworito are ok.And the field points in the -x direction. If you imagine a test charge Q(>0] at point P, this test charge will be repelled by the (+q) charge with a force that has an intensity of KqQ/d^2; this force is in +q -> Q...
19. ### In what direction should the plane head?

is nrqed online again?
20. ### In what direction should the plane head?

All your calculations are ok. bye
21. ### Crate motion question

Hi Hollysmoke, Since the 20 kg crate is in front of the 12 kg crate, the 12kg crate must push the other crate with a force that is sufficient to communicate an acceleration of 1.75 m/s^2. Force that must act on the 20 kg crate must be equal to it's mass times its acceleration = 20kg x 1.75...
22. ### For every action there is an equal and opposite reaction

In jet engine there is not realy a force acting by the gas on the jet. One of the great consequences of Newton's third law is that in a system, the net momentum (mass time velocity) is conserve. And one consequence of the momentum conservation is that jet propulsion is possible. Before the...
23. ### Directions of velocity and acceleration

Speed or velocity? speed is magnitude of the velocity vector. So speed is always a positive quantity. Now along a line we define the acceleration as a =(vf-vi)/t, (or delta t). Along a line you define a positive and a negative sens. if along this line a > 0 then the object is spreeding up...
24. ### QM probability

Your result for A is right. You have to understand the meaning of Psi. If, at the instant t, a measurement is made to locate the particle associated with the wave function Psi(x,t), the the probability P(x,t)dx that the particle will be found at a coordinate x and x+dx is equal to...
25. ### Algebra or PDEs?

Clearly you should take the PDE course. And if it is possible a course introducing you in differential geometry, that will give you a good basis in your study of general relativity. Dont do relativity in a too abstract way. Do physics first. If possible read Einstein text in general...
26. ### Calculus Rate of Change Help

Y may be know that the slope of the tangent is given by the value of the derivative at the pooint (-1, 5) . Knowing the slope, you will be able to determine the equation of the line. 2) You must know the rate of change of the radius. Do you know how to calculate the surface area of a sphere in...
27. ### Classical atom instable?

Hi, il classical electrodynamics, we learn that an accelerated charge emits light. So an electron orbiting in a keplerian orbit do have an acceleration, than must emits continuously light, than again losing energy. So the elctral would spirals down into the nucleus. N. Borhs elaborate a first...
28. ### Quick question

Remember that each time you take de derivative, the exponent reduces by one. And the derivative of a constant is zero. Ciao
29. ### Series and Sequence,

your second equation is wrong. it should read 5a + 35d = 235; after that you can solve the system formed withthis equation et your first equation to find a and d After that it should be easy to find the sum of the first 20 terms.
30. ### Finding root

Do you know how to solve x^2 + 2 = 0 ? and x^4 + 4 = 0? Look at the first one. (x+i√2)(x-i√2)=0 What for the second x^4 + 4=x^4+4x^2+4-4x^2; maybe you can continue and find your answer