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  1. W

    Stargazing Question on Refractor Telescope !

    And one last question, why the image is inverted ? which is up side down
  2. W

    Stargazing Question on Refractor Telescope !

    Thanks all ! Now i'm start building it
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    Stargazing Question on Refractor Telescope !

    Thanks ! But i couldn't find the answers for my questions from that. Help please ?
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    Stargazing Question on Refractor Telescope !

    I am plan on building a small refractor telescope about 20 cm long, i need your guys help ! 1. What len is use for Objective len and what len is use for Eyepiece len ? (how is it look like) 2. How far should i place objective len and eyepiece len apart ? 3. If i make a 20 cm long refractor...
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    KE and PE Work

    #1 No, I haven't studied the dot product yet A) HOw much work is done by the gravitational force ? b) Ho much work is done by 100 N force ? c) What is the change in kinetic energy of the crate ? d) What is the speed of the crate after it is pulled 5 m? Sorry about that
  6. W

    KE and PE Work

    #1 A 10kg crate is pulled up a rough incline with an initial speed of 1.5 m/s. The pulling force is 100Nparallel to the incline, which makes an angle of 20* with the horizontal. If the coefficient of kinetic friction is .40 and the crate is pulled a distance of 5 m. a)HOw much work is done by...
  7. W

    Acceleartion and Force again !

    Not cover momentum yet. but that was great. Thank a lot learning physics.
  8. W

    Acceleartion and Force again !

    OK, it was tricky ! And i was confused, how come the part a was so easy. Usually we use F=ma to find the acceleration when the problem involved with mass.
  9. W

    Acceleartion and Force again !

    F_net (acting on the rocket) = 9000 (14.3) = 128700 N F_net (rocket) = F_net (gas) (From your hints if this two force were equal, then how come the rocket laugh forward) 128700 = 740 a a = 173.9 m/s2 Is this right ?
  10. W

    Acceleartion and Force again !

    Problem 1 a) how come it is so easy ? b) got a little confuse, there only force of gravity is act on it.
  11. W

    Acceleartion and Force again !

    #1 Is that hints for part b #2 F_apply = 30921.6 N #3 Is that mean I was going on the right track right ? F_apply = 262.9 N a) the box moves b) F_friction = .12 (815.7) = 97.9 N F_x = 310cos32 - 97.9 = 164.9 N F = ma 164.9 = 100a a = 1.65 m/s2 25 = (1/2)(1.65)t2 t = 5.5 s Am i doing right ?
  12. W

    Acceleartion and Force again !

    #1 Ricky is on a rocket ship far from any planet or sun. The 900kg rocket fires its rockets for 3.5s sec and goes from 0m/s to 50 m/s.(a)What acceleration does the rocket undergo ?(b) If 160 kg of gas is expelled from the rocket. what is the gasses acceleration ? ------------------ vi = 50...
  13. W

    Acceleration coefficient

    Yes ... thanks learningphysics
  14. W

    Acceleration coefficient

    ok, I got this a = 3.3 m/s2
  15. W

    Acceleration coefficient

    F (friction) = .25 time 7 = 1.75
  16. W

    Acceleration coefficient

    in this problem, there are only 2 force make the block able to slid. (and it is force of gravity on 12 kg and force friction on 7 kg. So F net = F (gravity) - F (fiction)
  17. W

    Acceleration coefficient

    Find the acceleration experienced by each of the two masses shown in the picture below if the coefficient of friction between the 7 kg mass and the plane is .25 ? ------------ In the picture, is the force of fiction go that way ? http://img515.imageshack.us/img515/893/img3394dj7.jpg [Broken]...
  18. W

    Coefficient of friction of box of books

    F (parallel) = 172.9 N Fnet = 400 - 172.9 -> 227.1 N F = ma --> a = 7.4 m/s2 t = 1.04 s still wrong ?
  19. W

    Coefficient of friction of box of books

    Problem 1: A box of books weighting 300 N is shoved cross the floor of an apartment by a force of 400 N exerted downward at an angle of 35.2* below the horizontal. If the coefficient of kinetic friction between box and floor is .57, how long does it take t move the box 4 m, starting from rest ...
  20. W

    Force - Scale - Tension

    Can you give me some hints for problem 2 please ?
  21. W

    Force - Scale - Tension

    #1 On takeoff, the combined action of the engines and wings of an airplane exerts an 8000N force on the plane, directed upward at an angle of 65* above the horizontal. The plane rises with constant velocity in the vertical direction while continuing to accelerate in the horizontal direction...
  22. W

    What force ?

    Totally got no idea
  23. W

    What force ?

    #1 A 5 g bullet leaves the muzzle of a rifle with a speed of 320 m/s. What force (assumed constant) is exerted on the bullet while it is traveling down the .82 m long barrel of the rifle ? -------------------------- m = .005 kg v (initial) = 320 m/s d = .82m F = ma but i don't know how to find...
  24. W

    Magnitude - Distance

    #1 mag = 429.5 N acc is NorthEast with the value 1.6 m/s2 #2 OH, i forgot that equation ! Forgot to think of the term displacement ! d = 1.5 m Is that correct ?
  25. W

    Magnitude - Distance

    #1 So the magnitude is the same as the resultant ! #2 I only know to the Newton 2nd Law
  26. W

    Magnitude - Distance

    [SOLVED] Magnitude - Distance #1 The force of the wind on the sails of a sailboat is 390 N north. The water exerts a force of 180 N east. If the boat (including crew) has a mass of 270 kg, what are the magnitude and direction of its acceleration. --------------------------------- 390 N...
  27. W

    The Law of Motion

    Is that the acceleration is 0, and i don't really know what is net force is ? That why i asked
  28. W

    The Law of Motion

    An 850 kg car is moving to the right at 1.44 m/s. What is the net force on the car ? I am totally off on this problem ! Can someone help ? And in the problem above, it is different when the car moving left ? Thanks
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