14 January 2014

Physics Homework Chapter 15

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1.  A 7.66 nC charge is located 1.87 m from a 4.46 nC point charge.

(a) Find the magnitude of the electrostatic force that one charge exerts on the other.
 ______ N

(b) Is the force attractive or repulsive?





2. A charged particle A exerts a force of 2.55 μN to the right on charged particle B when the particles are 13.0 mm apart. Particle B moves straight away from A to make the distance between them 16.9 mm. What vector force does particle B then exert on A?
_____ μN to the left





3.A small sphere of mass m = 7.60 g and charge q1 = 29.9 nC is attached to the end of a string and hangs vertically as in the figure. A second charge of equal mass and charge q2 = −58.0 nC is located below the first charge a distance d = 2.00 cm below the first charge as in the figure.

(a) Find the tension in the string.
_____N

(b) If the string can withstand a maximum tension of 0.180 N, what is the smallest value d can have before the string breaks?
_____cm


















4. A small sphere of charge q1 = 0.808 µC hangs from the end of a spring as in figure (a). When another small sphere of charge q2 = −0.612 µC is held beneath the first sphere as in figure (b), the spring stretches by d = 3.78 cm from its original length and reaches a new equilibrium position with a separation between the charges of r = 5.15 cm. What is the force constant of the spring?
_____N/m









5. Calculate the magnitude and direction of the Coulomb force on each of the three charges shown in the figure below.








6.00 µC charge:
magnitude
_____N direction

1.50 µC charge:
magnitude
_____N direction

−2.00 µC charge:
magnitude
_____N
direction





6. A small object of mass 3.82 g and charge -18.4 µC is suspended motionless above the ground when immersed in a uniform electric field perpendicular to the ground. What are the magnitude and direction of the electric field?

magnitude
_____N/C
direction





7. An electric field of magnitude 5.25  105 N/C points due west at a certain location. Find the magnitude and direction of the force on a −4.20 µC charge at this location.

magnitude    
_____N
direction





8. An electron is accelerated by a constant electric field of magnitude 315 N/C.

(a) Find the acceleration of the electron.
_____m/s^2

(b) Use the equations of motion with constant acceleration to find the electron's speed after 9.50  10-9 s, assuming it starts from rest.
_____m/s





9. A proton accelerates from rest in a uniform electric field of 600 N/C. At some later time, its speed is 1.38  106 m/s.

(a) Find the magnitude of the acceleration of the proton.
_____m/s2

(b) How long does it take the proton to reach this speed?
_____µs

(c) How far has it moved in that interval?
_____m

(d) What is its kinetic energy at the later time?
_____J

3


Before beginning on Problem #10, it may be useful to watch a video that explains vector notation
vector notation is the use of the symbols "î and ĵ" to indicate a direction (apart from a magnitude).


10. Three point charges are located on a circular arc as shown in the figure below. (Let r = 3.76 cm. Let to the right be the +x direction and up along the screen be the +y direction.)















(a) What is the total electric field at P, the center of the arc?
             →
 (Vector)E = ______ î  +  _____ ĵ

(b) Find the electric force that would be exerted on a −4.8 nC point charge placed at P.
              →
 (Vector) F = _____ î + _____ ĵ






11. In the figure below, determine the point (other than infinity) at which the total electric field is zero.

_____m to the left of −2.5 × 10−6 C charge





12. A uniform electric field of magnitude E = 410 N/C makes an angle of θ = 66.0° with a plane surface of area A = 4.00 m2 as in the figure below. Find the electric flux through this surface.

_____N · m2/C













NOTE: in video #12, I make a claim that I think the textbook misrepresents the facts. After looking a second time, I feel I may have actually misinterpreted the textbook. The explanation in the textbook is actually correct (if read in the entirety -- and read slowly).


13. An electric field of intensity 4.5 kN/C is applied along the x-axis. Calculate the electric flux through a rectangular plane 0.350 m wide and 0.700 m long if the following conditions are true.

a. The plane is parallel to the y-z plane
_____ N*m2/C

b. The plane is parallel to the x-y plane
_____ N*m2/C

c. The plane contains the y-axis, and its normal makes an angle of 35° with the x-axis
_____ N*m2/C

16 comments:

  1. Great site! This is always helpful to the problems I have in physics.

    ReplyDelete
  2. What happened to the video for problem #5 ?

    ReplyDelete
    Replies
    1. Hopefully that fixes #5. Thanks for letting me know.

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  3. Thanks! Excellent videos

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    Replies
    1. Appreciate it! Let me know if there is anything I can do better (besides my handwriting)

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  4. Thank you so much! As a BioChem major I am very grateful for all your help.

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    Replies
    1. It's my pleasure. The only thing I could ask is that you spread the word!

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  5. Thanks so much. The equations from physics 1 helps put all of this together in a very understandable way.

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  6. Thanks Mike!! You're awesome!

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  7. This comment has been removed by the author.

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  8. The excellent tutorials around there which will almost give you so much confidence to go and complete all of your projects and assignments which nearly needs to be completed in order to survive to be professional, also there are many other perceptional ideas which will although assist at the right time. help with physics homework problems

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  9. Hey Mike, I am subscribed to your channel on Youtube and have used your website before. I am just wondering is this where I come if I have questions on certain material you have covered? If so, could you explain why certain values for Coulomb's law ( I think) are given the x10^-9 x10^-6 x10^3 , but the original problem just gives the numbers as whole numbers. Also how do you figure out which of the given original problem values are tailed with either one of these (ex: x10^-9 x10^-6 x10^3)?? Thanks for your help! Your channel is something I can always rely on!

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    Replies
    1. OHHH nevermind, i got it. It's just that the book doesn't have the problems using the metric system, so you have to convert g ---> kg etc.

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