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  1. S

    Half Life for patient

    Homework Statement Ok so I'm doing this practise problem but I have no clue what to do. "A radioactive sample intended for irradiation of a hospital patient is prepared at a nearby lab. The sample has a half-life of 83.61 h. What should it's initial activity be if it's activity is to be...
  2. S

    Potential Energy and Spring

    that's what I got to the first time, but it was wrong...
  3. S

    Potential Energy and Spring

    Homework Statement A block of mass m = 3.4 kg is dropped from height h = 44 cm onto a spring of spring constant k = 1920 N/m (Fig. 8-38). Find the maximum distance the spring is compressed. [PLAIN]http://edugen.wiley.com/edugen/courses/crs1650/art/qb/qu/c08/fig08_36.gif [Broken]...
  4. S

    Work Done by a Spring Force and block problem

    PE is just PE = 1/2kx^2 but how do we find k? 160N/0.16m = k ?
  5. S

    Work Done by a Spring Force and block problem

    Homework Statement http://edugen.wiley.com/edugen/courses/crs1650/art/qb/qu/c07/pict_7_36.gif gives spring force Fx versus position x for the spring–block arrangement http://edugen.wiley.com/edugen/courses/crs1650/art/qb/qu/c07/pict_7_11.gif The scale is set by Fs = 160 N. We...
  6. S

    How do you find the Natural Log of a Number?

    Title says all.
  7. S

    What is the magnitude of the frictional force?

    strictly horizontal why do you ask?
  8. S

    What is the magnitude of the frictional force?

    Homework Statement A person pushes with force of 220N on a 40 kg create. The coefficent of kinetic friction of 0.35. What is the magnitude of the frictional force? Homework Equations Ff = uN The Attempt at a Solution so do I just go Ff = 0.35*(40kg)(9.81m/s^2)...
  9. S

    Newtons Law

    Homework Statement The velocity of a 6 kg particle is given by v = (5ti + 4t2j ) m/s, with time t in seconds. At the instant the net force on the particle has a magnitude of 43 N, what are the direction (relative to the positive direction of the x axis) of (a) the net force and (b) the...
  10. S

    Projectile Motion wind acceleration

    So once I find Vy I use Vx^2 + Vy^2 = V^2?
  11. S

    Projectile Motion wind acceleration

    Homework Statement A moderate wind accelerates a pebble over a horizontal xy plane with a constant acceleration a = (6i + 7j)m/s^2 . At time t = 0, the velocity is (3i)m/s . What are the (a) magnitude and (b) angle of its velocity when it has been displaced by 12.0 m parallel to the x axis...
  12. S

    Projectile Motion

    I have 2 question. 1) In projectile motion is the velocity in the x compontent constant, while above the release point? 2) Is Y = Voy * t - 0.5 * 9.81 * t^2 the equation used to find the heigth at any given time? Thank You.
  13. S

    Question about projectile motion

    I have another question what equations can I use to find intial v, the angle and maximum height on projectile motion?
  14. S

    Question about projectile motion

    I have a question when any object is in project motion is the vertical acceleration of the object equal to 9.81m/s^2 (gravity)?
  15. S

    Constant Acceleration of a train

    We've learn like only 3 formulas if this isn't it I don't know what it is. Can someone tell me what forumla to use?
  16. S

    Constant Acceleration of a train

    I think I know now v^2 = vi ^2 * 2a (x-xo) do u use this formula?
  17. S

    Distribution Curve in excel

    Hi I'm trying to make a distribution curve in excel, but I can't seem to find it. I have excel 2003 I know how to make column graphs and stuff, but I can't seem to find where to find how to make a distribution curve can anyone help me? Here is a link of the type of graph I want to make...
  18. S

    Constant Acceleration of a train

    how would I do that if I don't have the time?
  19. S

    Constant Acceleration of a train

    Homework Statement When a high-speed passenger train traveling at 158 km/h rounds a bend, the engineer is shocked to see that a locomotive has improperly entered onto the track from a siding and is a distance D = 699 m ahead. The locomotive is moving at 27.2 km/h. The engineer of the...
  20. S

    Looking for help with physics vectors

    Homework Statement Let v = (-1,2,5) Find all scalars k such that llkvll = 4 The Attempt at a Solution I don't know what to do please help Homework Statement Homework Equations The Attempt at a Solution
  21. S

    Homogeneous system

    Homework Statement Let A * x= 0 be a homogeneous system of n linear equations in n unknowns, that has only the trivial solution. Show that if k is any postive integer, than the system A^k * X = 0 also has only the trivial solution. The Attempt at a Solution I'm so lost please help...
  22. S

    Can we have infinite energy?

    please explain?
  23. S

    Can there be infinite energy?

    It seems that our perception of time is inter-related to the loss of energy and order over time. If infinite regress were true when that means infinite energy right? So can we have infinite energy? Is there infinite regress? Can we even have infinite energy?
  24. S

    Can we have infinite energy?

    Homework Statement The question I have is, is can we have infinite energy? The Attempt at a Solution I've tried thinking about this. It seems that our perception of time is inter-related to the loss of energy and order over time. If infinite regress were true when that means...
  25. S

    Sum of invertible matrices is invertible?

    Homework Statement Is the sum of two invertible matrices necessarily invertible? The Attempt at a Solution I don't know please help.
  26. S

    I need to extract a divisor

    Ok this is what I did int n; cout << enter number; cin >> n; for (int i = 1 ; i < n ; i++ ) if ( n % i == 0 ) I could use some help please like how to I extract the divisor? so I can add them. Thanks a lot.
  27. S

    Making a number to decimal form

    Here is what the excerise says One such command displays fractions. For example 5/4 is entered "\frac{5}{4}". Write a computer program that simulates a \frac{}{} command. The program reads two integers n1 and n2 EXAMPLE 1: Enter fraction in the form n1/n2: 5/4 ...
  28. S

    Making a number to decimal form

    I'm doing an excerise to make factions, but I need to simulate a \frac{}{} command. To display numbers in faction AND decimal form. How do I simulate a \frac{}{} command? Thanks. Like I have to prompt the user. int denominator, numerator; scanf("\\frac{%d}{%d}", &numerator...
  29. S

    C/C++ (C++) How would I display a value rounded to the nearest integer?

    Like for example Prompting message reads. "Please enter a positive value" Example: Please enter a positive value: 234.7 Rounded to the nearest integer the number is: 235 Please enter a positive value: 10.3 Rounded to the nearest integer the number is: 10 What I have...
  30. S

    C/C++ The following C++ program does not compile

    cout << "2 + 3 * 5 = " 2+3*5 << endl; do I just need to put it as cout << "2 + 3 * 5=" << (2+3*5) << endl;
  31. S

    Bohr Moedl

    Homework Statement Determine the wavelenghts of photons given off for the 3rd line in the Lyman series, the 2nd line in the Balmer series and the 1st line in the Paschen series. The Attempt at a Solution Lyman series: n=1 Balmer series: n=2 Paschen Series: n=3 What do I do?
  32. S

    Photoelectric Effect.

    How many photons per second are emitted by a monochromatic light bulb (650nm) that emits 25 W of power? W=hfo hf=Ek + W P=W/t is there a way we can find power? how do I solve this question?
  33. S

    Cathode Ray Tube

    Homework Statement A positively charged particle of mass 7.2 * 10^-8kg is traveling east with speed of 85 m/s. The particle enters a 0.31 T uniform magnetic field, and 2.2 * 10^-3 secounds later leaves the field one-quarter south with speed of 85 m/s. What is the charge of the particle and...
  34. S

    Turbine producing current - Ohmic heating

    Homework Statement The turbine produces current that is at 12kV. To lessen the problem of Ohmic heating, a transformer steps up the voltage to 138kV for power line tranmission. Homework Equations Np/Ns=Vp/Vs ?
  35. S

    Magnetic Fields and Forces

    Homework Statement Prove that the time for one revolution of a charged particle moving perpendicular to a uniform magnetic field is independent of it's speed. Write an expression that gives the period T in terms of the mass and charge of the particle and the magnetic field strength...
  36. S

    Magnetic Field (Fc)

    Homework Statement How would I find how long it takes for an alpha particle to move halfway through a complete circle? Homework Equations Fc=mv^2 Ft=mv The Attempt at a Solution if they gave me speed how would I find how much it traveled?
  37. S

    Magnetic Field and Forces

    I'm lost don't I use my palm to find force? My palm is magnetic force not field.
  38. S

    Magnetic Field and Forces

    I'm confused don't I use left hand rule when dealing with electrons?
  39. S

    Magnetic Field and Forces

    Homework Statement At a point near the equator, the Earth's magnetic field is horizontal and points to the north. If an electron is moving vertically upward at this point, what is the direction of the magnetic force acting on this? Explain.
  40. S

    Related Rates (differentiating)

    Homework Statement How fast is the area of a square increasing when the side is 3 meters in length and growing at a rate of 0.8meter/minute? Homework Equations SA=LW L=3 dL/dt=0.8 The Attempt at a Solution I have no clue how to start this and I'm bad at word problems.
  41. S

    Kirchoff's Law

    Homework Statement How do I prove the relationship between the equivalent resistance of a parallel circuit and the values of the constituent resistors exist? Homework Equations V=IR The Attempt at a Solution Is it because: I total= I1+I2+I3 and V is the same in parallel...
  42. S

    Parallel and Series Circuits

    When drawing Parallel and Series Circuits when differences are there? Like are there differences in voltmeter and amp meter what differents are there when drawing?
  43. S

    Line Tangent ro a Parabola

    So I take the slope of this? 3x + 2y = 7 so... 2y = -3x + 7 y= -3/2x + 7/2 slope = -3/2 so if it is perpendicular the slope is 2/3 is that my right slope? I now I have to do more but it that right so far?
  44. S

    Line Tangent ro a Parabola

    Homework Statement Find the point on the parabola y= 4x^2 + 2x - 5 where the tangent line is perpendicular to the line 3x + 2y = 7. Homework Equations The Attempt at a Solution I don't know what to do since I was away the last 3 classes since I was away. Help me please.
  45. S

    Series Circuit

    Homework Statement A 47 resistor can dissipate up to 0.25-W of power without burning up. What is the smallest number of such resistors that can be connected in series across a 9.0-V battery without anyone of them burning up> Homework Equations V=IR P=IV The Attempt at a Solution I...
  46. S

    Electric Fields

    Homework Statement A charge of 3.5*10^-6 is fixed on the x-axis at x= 0.55m, while a charge of -15*10^-6 is fixed at the origin. What is the net electric field on the x-axis at 0.8m? Homework Equations Fe = qE The Attempt at a Solution Used Fe = qE, but that's it.
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