A billboard, mass 15 kg, is suspended from a roof by means of a light inextensible string. Force F pulls the billboard sideways, as shown in the diagram below.
40°
string
F
15 kg
When the angle between the roof and the string is 40°, a closed vector diagram is
obtained for all the forces acting on the billboard. What deduction can be made when the forces acting on an object forms a closed vector diagram?

​

Do you agree with scientist’s prediction about the warming of alaska and other polar regions?

A3.9 g aluminum foil ball with a charge of +4.1×10−9 c is suspended on a string in a uniform horizontal e⃗ field. the string deviates to the right and makes an angle of 30∘ with the vertical. part a part complete what information about the e⃗ field can you determine for this situation? what information about the field can you determine for this situation? only the magnitude of e⃗ only the direction of e⃗ both the magnitude and the direction of e⃗ none of the above previous answers correct part b determine the magnitude of the electric field. express your answer with the appropriate units. e e = nothing nothing request answer part c determine the direction of the electric field. determine the direction of the electric field. to the right to the left away from you toward you

Explain why electric current cannot exist if a current doesn't have a voltage source.