soal-soal fisika

 

1.      Explain this equation to get its physic meaning’s!

ANSWER:

This equation explain the potential gradient in three dimensions. In three dimensions, Cartesian coordinates make it clear that the resultant potential gradient is the sum of the potential gradients in each direction:

Where  are unit vectors in the x, y, z directions. This can be compactly written in terms of the gradient operator

 , although this final form holds in any curvilinear coordinate system, not just Cartesian.

This expression represents a significant feature of any conservative vector field F, namely F has a corresponding potential ϕ.

 

 

 

2.      Mention all kinds of potential energy. Give a brief explanantion using its formula!

ANNSWER:

Mechanical Potential Energy

            Mechanical energy is the energy of movement. All items have potential energy based on their position (gravitational potential energy) and ability to bounce (elastic potential energy). When the potential energy of an object is combined with its kinetic energy, it results in mechanical energy. EX. a yoyo before it is released, River water at the top of a waterfall, a book on a table before it falls.

Elastic Potential Energy

            The material an item is made of can affect its potential energy as well. An elastic ball has higher elasticity than a bowling ball; therefore, it will bounce higher with the same amount of force. Ex. A stretched rubber band, soccer balls before players kick them, a diving board just before someone dives.

Electric Potential Energy

            When you see a light switch that’s off, you can’t see the charge that’s waiting to flow through the wires. That’s just one example of electric potential energy. Ex. An incandescent light bulb that is turned off,  car's headlights before they are turned on, a radio tower that is not working.

 

3.      Electron with a speed of enters a region where there is a uniform electric field with E = 500 N/C. (a) Show that gravitational influences can be neglected in this situation. (b) If, after traveling for some distance d in the field, the electron comes to rest for an instant, in which direction is the field? (c) Calculate d.

ANSWER:

 

.we know g = 9.8 m/s²

                M = 9.11 x 10^-31 kg

. (a) The magnitude of the force applied to the electron by the field is F = qE . Dividing by the mass gives the magnitude of the acceleration of the electron:

 

. a =  =  =  = 8.78 x 10¹³ N/kg

 

.(b) To stop the electron, the force on the electron from the field must be directed opposite to the electron’s initial velocity. Because the electron has a negative charge, the field and force are in opposite directions. Thus, the electric field must be in the same direction as the electron’s initial velocity.