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  1. M

    Calculating mass of two stars when ratio of distances to center of mass is known

    thanks for the help i used P^2/a^3 = 4 pi^2/ MG to get the mass
  2. M

    Calculating mass of two stars when ratio of distances to center of mass is known

    ok so i got the reduced mass now i know that the formula for reduced mass is m1 + m2 / m1m2 but i don't really know where to go from here what I am having trouble understanding is where the parallax and ratio of distances comes in
  3. M

    Calculating mass of two stars when ratio of distances to center of mass is known

    Homework Statement we are looking at two stars in the eridani system, eri B and eri C. the period of the system is 247.9 years. the system's measured trigonometric parallax is 0.201 arcseconds and the tru angular extent to the semimajor axis of the reduced mass is 6.89". the ratio of...
  4. M

    Astrophysics- unresolved binary star system

    Homework Statement Consider an unresolved binary star at a distance of 500pc consisting of an A1V dwarf and a K0III giant star. compute mb and mv and B-V for this object we know the mass, luminosty, radius, Mbol , Mv, Te , and B-V for each individual star. Homework Equations...
  5. M

    News No military option against the Iranian nuclear program

    sorry but how do you know they have antisemitic media, classic-style antisemitic cartoons? and only the ahmadinejad denies it not the government
  6. M

    Protons delivered per second in a proton beam

    Homework Statement a 5.0 mm-diameter proton beam carries a total current of 1.5mA. the current density in the proton beam, which increases with distance from the center, is given by j=j(edge)(r/R), where R is the radius of the beam and j(edge) is the current density at the edge. a) how many...
  7. M

    Electric potential of a wire

    thanks allot for the help
  8. M

    Electric potential of a wire

    Homework Statement the wire in the image below has a linear charge density \lambda . what is the electric potential at the center of the semicircle? http://img18.imageshack.us/img18/5139/physicsproblem.jpg [Broken] Homework Equations The Attempt at a Solution i know that the potential from...
  9. M

    Spinning rod dropping on a pivot

    Homework Statement a long, thin rod of mass M and length L is standing stright up on a table. its lower end rotates on a frictionless pivot. a very slight push causes the rod to fall over. as it hits the table, what are (a) the angular velocity and (b) the speed of the tip of the rod...
  10. M

    Hollow sphere rolling up a ramp

    v=\omegar right? but we don't have the radius of the sphere or do we....?
  11. M

    Hollow sphere rolling up a ramp

    Homework Statement a hollow sphere is rolling long a horizontal floor at 5 m/s when it comes to a 30 degree incline. how far up the incline does it roll before reversing direction? Homework Equations The Attempt at a Solution it seems like conservation of energy would work best for this...
  12. M

    Inelastic collision of a projectile with a pendulum

    im having problems dealing with the angle of the pendulum as it spins if we have the y-axis in the direction of centrifugal force the sum of the forces would be: ma = 400N - mgCos(angle) could i consider the ball when its at a 90 degree angle to get rid of that thing and at what point in...
  13. M

    Inelastic collision of a projectile with a pendulum

    Homework Statement a 20 kg wood ball hangs from a 2.0 m long wire. the maximum tension the wire can withstand without breaking is 400 n. a 1.0 kg projectile traveling horizontally hit and embeds itself in a the wood ball. what is the largest speed this projectile can have without causing the...
  14. M

    Ball rolling in a bowl problem

    Homework Statement a small ball slides , with constant speed (a\theta tangential acceleration = 0) , around a horizontal circle at height h inside a firctionless, hemispherical bowl of radius R. derive a formula for the balls angular velocity \omega in terms of the radius of the radius of the...
  15. M

    Rocket attatched to a spring problem

    Homework Statement a 10.2 kg weather rocket generates a thrust of 200N. the rocket ,pointing upwards, is clamped to the top of a vertical spring, whose spring constant is 500N/m and is anchored to the ground a)initially before the engine is ignited the sits at rest on top of the srping. how...
  16. M

    Collision of a block with a spring

    Homework Statement a 100g block on a frictionless table is firmly attached to one end of a spring with k = 20 N/m. the other end of the spring is anchored to the wall. a 20g ball is thrown horizontally toward the block with a speed of 5.0 m/s. assuming that the collision is perfectly inelastic...
  17. M

    The weight of two blocks

    thanks for the help one more thing how come the vertical component of the normal force doesn't affect the wedge when the blaock is standing still?
  18. M

    The weight of two blocks

    Homework Statement say we have a block resting on a incline of a wedge (the incline is 40 degrees). the wedge is on a scale(mass of block is .2 kg and mass of wedge is .8kg).if the block is at rest (due to to static friction) the scale would read 9.8N. but let's say we eliminate the friction...
  19. M

    Quick error propagation problem

    thanks allot!:smile:
  20. M

    Quick error propagation problem

    Homework Statement we are trying to find the x -component of a velocity vector (V*cos\theta) our uncertainty for the velocity is +-.0003 and for the and it is .5(in degrees) how do we propagate the error for this v=.048 while \theta =27 degrees Homework Equations The Attempt...
  21. M

    Block being pushed along the floor (dynamics problem)

    Homework Statement a block pushed along the floor with velocity V0 slides a distance d after the pushing force is removed. a) if the mass of the block is doubled but the initial velocity is not changed what is the distance the block slides before stopping? b) if the initial velocity of the...
  22. M

    Integration problem

    Homework Statement find the indefinate integral of 1+x2/(1+x4) Homework Equations The Attempt at a Solution im having trouble trying to figure what to use to substitute into this equation
  23. M

    Finding acceleration of elevator using mass

    Fn = mg (for the first part) m= Fn/ g is that the mass? the units don't really match though and what do i substitute in for mg ? 150 lbs?
  24. M

    Finding acceleration of elevator using mass

    Homework Statement one day you take your bathroom scale with you into an elevator. the scale reads 150 lbs as the door closes. the reading varies between 120 lbs and 170 lbs as the elevator travels up. what is the acceleration of the elevator while its accelerating and decelerating...
  25. M

    Bullet penetrating a block problem

    oops guess i better double check that thanks for the help :biggrin:
  26. M

    Bullet penetrating a block problem

    dont worry i haven't forgotten about the other equations :) i was just wondering why this one didnt work
  27. M

    Bullet penetrating a block problem

    Homework Statement a rifle with a barell length of 60 cm fires a 10g bullet with a horizontal speed of 400 m/s. the bullet strikes a block of wood and penetrates to a depth of 12 cm. how long does it take the bullet to come to rest( from when it penetrates the block to when it stops)...
  28. M

    Question about vertical and horizaontal

    question about "vertical" and "horizaontal" Homework Statement the terms "vertical" and "horizontal" are frequently used in physics. give operational definitions for these two terms. an operational definition defines a term by how it is measured or determined. your definition should apply...
  29. M

    Quick question about enzyme allosteric inhibition

    yes i do i was thinking it would cause them both to go to zero if it inhibition?
  30. M

    Quick question about circular motion

    so if the centripetal acceleration is constant then angular and tangential acceleration are zero? thanks for the help!
  31. M

    Quick question about circular motion

    lets suppose the radius is constant but the centripetal acceleration vector is getting smaller what would happen to the other 2 accelerations?
  32. M

    Quick question about circular motion

    what is the relation between the centripetal acceleration, angular acceleration and tangential acceleration in circular motion? for example if the centripetal acceleration vector is getting larger for an object in circular motion does this mean something is also happening to the tangential...
  33. M

    Circular motion problem

    Homework Statement if you step on your car's breaks hard, the wheels stop turning after 1.0 revolution. At the same constant acceleration , how many revolutions do the wheels make before stopping if you initial speed is twice as high? Homework Equations The Attempt at a Solution im having...
  34. M

    Quick question about enzyme allosteric inhibition

    lets say an enzyme is inhibited by something binding to its allosteric site. what effect would this have on the enzymes Km and Vmax?
  35. M

    Question about unknown type of metal ion

    oops sorry to include that its a 1.0M solution cuso4
  36. M

    Question about unknown type of metal ion

    Homework Statement we are mixing CuSo4 (Cu2+) with an iron (Fe) powder and we are trying to determine whether Fe2+ forms or Fe3+ now the question is : suppose that 1.0 g of iron is used in the experiment. what is the minimum volume of Cu2+ solution that must be added in order to completely...
  37. M

    Finding molar mass of unknown element

    Homework Statement element X reacts with oxygen to produce a pure sample of X2O3 . in an experiment, it is found that 1.0g of X produces 1.1596g of X2O3 . what is the molar mass of X? Homework Equations The Attempt at a Solution well we can write a equation for it 4X + 3O2 --->...
  38. M

    Kinematics equations with collision fo 2 balls

    Homework Statement a ball is shot straight up from the ground with speed Vo. simultaneously, a second rubber ball at height h directly above the first ball is dropped from rest at what height above the ground do the balls collide?asnwer should be a symbolic expression in terms of Vo and g...
  39. M

    Kinematics problem

    do we assume that Vi of the rocket is zero?
  40. M

    Kinematics problem

    actually you don't have the bolts velocity
  41. M

    Kinematics problem

    Homework Statement a rocket is launched straight up with a constant acceleration. four seconds after takeoff , a bolt falls off the side of the rocket. the bolt hits the ground 6.0 seconds later. what was the rockets acceleration? Homework Equations any kinematics equations The Attempt at a...
  42. M

    Quick question about uncertainty calculation

    Homework Statement lets say we have A * B A=12.8 + 0.2 B=3.75 + 0.08 how would we calculate the new uncertainty value ive seen soo many ways of doing this I am a bit confused thanks in advance Homework Equations any equation used to calculate uncertainty The Attempt at a Solution...
  43. M

    Gas laws problem (need quick help )

    gas laws problem (need quick help please) Homework Statement ill try to describe the situation as best i can at first we have a flask (150 ml) with 0.1g of NaHCO3 we attach a syringe with 20ml of acetic acid (CH3COOH ) to it (and seal it off so nothing escapes) we inject the acetic acid...
  44. M

    Dimensional analysis question

    one more quick thing about dimensional analysis :) in an equation let's say X=Vit + 1/2 a t2 if we wanted to prove that this equation is dimensionally correct, how would the + between the 2 terms on the r.h.s effect the analysis would we have to ignore the + and just try to make it so that...
  45. M

    Dimensional analysis question

    just to clarify for b & d, does it matter that the dimensions are in the exponent?
  46. M

    Dimensional analysis question

    Homework Statement determin the dimensions of \alpha in the following a)Sin(\alphaX^{}2) (alpha* X squared) (X is a distance) b)10\alphat3 c)cot(\alphaX2/R) (R is a radius) d)e(hf/\alphaT - 1 (h is Plancks constant with units J*s) ( f is frequency Homework Equations The Attempt at a...
  47. M

    Stop Saying Everything Is An Illusion!

    if everything is an illusion then illusions must be real
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