What is Relative motion: Definition and 282 Discussions

The relative velocity







v
→




B
∣
A




{\displaystyle {\vec {v}}_{B\mid A}}
(also







v
→




B
A




{\displaystyle {\vec {v}}_{BA}}
or







v
→




B
rel
⁡
A




{\displaystyle {\vec {v}}_{B\operatorname {rel} A}}
) is the velocity of an object or observer B in the rest frame of another object or observer A.

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  1. P

    Is my relative motion analysis correct for this engineering problem?

    Homework Statement The attempt at a solution I used the concept of relative motion analysis for velocity: VB = VA + VB/A (4) = (-2) + ω(3) ω = 2 rad/s (CCW) Is this correct?
  2. H

    Comparing Ropes Released from Ships A and B in Relative Motion

    Suppose we have two ships A and B in uniform motion according to each other(A claims B to in motion and B claims A to be in motion). Let each one of the objects have a roll of rope on it (let us call the ropes a-> for A's rope and b-> for B's rope). Now when the ships were initially close to...
  3. L

    How Do You Calculate the Velocity of a Ball Thrown from a Moving Train?

    Homework Statement A man on a moving train throws a ball at a parked car. Find velocity of the ball when it hits the car if: train is moving 21 m/s North East; the man is walking 3.0 m/s [E35S] (relative to train) ball is thrown 10.0 m/s [W22S] (relative to man) Homework Equations VBG...
  4. T

    Why Is My Calculation for the Plane's Correct Heading Incorrect?

    Homework Statement A plane has an airspeed of 200 mph. The pilot wishes to reach a destination 600 mi due east, but a wind is blowing at 10.0 mph in the direction 10.0 degrees north of east. In what direction must the pilot head the plane in order to reach her destination? ______________...
  5. G

    Relative Motion: Moe's Corridor Walk Time

    Relative Motion: moving sidewalk! Homework Statement An airport terminal has a moving sidewalk to speed passengers through a long corridor. Larry does not use the moving sidewalk; he takes 140 s to walk through the corridor. Curly, who simply stands on the moving sidewalk, covers the same...
  6. E

    Relative Motion- Airplane vs radar station and tracking the displacement

    Relative Motion-- Airplane vs radar station and tracking the displacement In Figure 4-49, a radar station detects an airplane approaching directly from the east. At first observation, the airplane is at distance d1 = 340 m from the station and at angle θ1 = 34° above the horizon. The airplane...
  7. T

    Projectile and relative motion help

    Homework Statement A boy is standing on a long railroad car throws a ball straight upwards.The car is moving on a horizontal road with an accelaration of 1m/s^2. and the projection velocity is 9.8m/s.How far behind the boy will the ball fall on the car. Homework Equations Not entirely sure...
  8. 0

    Relative Motion - What is your thought process?

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  9. K

    Dynamics - Relative Motion Help?

    Homework Statement Conveyor belt A, which forms a 20° angle with the horizontal, moves at a constant speed of 4 ft/s and is used to load an airplane. Knowing that a worker tosses duffel bag B with an initial velocity of 2.5 ft/s at an angle of 30° with the horizontal, determine the velocity of...
  10. B

    Relative Motion: Solving Kinematic Problems with Multiple Moving Objects

    [PLAIN]http://img811.imageshack.us/img811/4435/relativemotion.jpg I'm having trouble on figuring out on how to go about this one. I know that I have to use the kinematic equations for each dimensions, find time, and set the x components equal to each other, but the relative velocity of...
  11. M

    How Fast is the Distance Between Two Ships Changing at 4:00 P.M.?

    Homework Statement At noon, ship A is 150 km west of ship B. Ship A is sailing east at 35 km h and ship B is sailing north at 25 km h. How fast is the distance between the ships changing at 4:00 P.M.? Homework Equations The Attempt at a Solution I did it using geometry and...
  12. B

    Dynamics (Kinematics) relative motion, HELP

    Homework Statement The bar AB is rotating with an angular velocity w=10rad/s. Determine the velocity of the piston C at the instant θ = 45. Provide the vector solution and the solution with the instantaneous center of zero velocity Homework Equations Vb = Va + w x r(b/a) Vc = Vb + w x...
  13. G

    How Does Relative Motion Affect What Barbara Sees While Rollerblading?

    This is a practice question. If somebody could help me with this practice question, I'd really appreciate it. Two friends, Barbara and Neil, are out rollerblading. With respect to the ground, Barbara is skating due south. Neil is in front of her and to her left. With respect to the ground...
  14. P

    How to Calculate Relative Motion with Given Positions and Velocities?

    Homework Statement I am given the location of 3 points in space: Z1= 3+3i Z2= 7+5i Z3= 5+5i and the velocity of two points: V_1= 8+0i V_2= 7+6i How do I find V3? Homework Equations V_1/2= V_1-V_2 V_3= V1+V_3/1 V_2/1= V_2-V_1 The Attempt at a Solution I have the...
  15. K

    What is the Required Heading of the Plane in a Crosswind?

    Relative Motion prob, please help Homework Statement A pilot of an plane has to get to a point 320 km due North in 1 hour. Ground Control reports inform that there is a cross wind of 80 km/h towards 37o South of West. What is the required heading pf the plane? Homework Equations VPE =...
  16. K

    Finding the Speed of Rain in Relative Motion

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  17. C

    Relative motion of a swimmer crossing a river

    A swimmer can swim at 2.0 m/s in still water. She attempts to swim due north across a river flowing eastward at 1.5 m/s. a) What is her velocity relative to the ground? b) Suppose she wants to arrive directly across from her starting point. In what direction must she head? What will be her...
  18. S

    Relative motion and displacement

    Homework Statement a man walks 600m [E47 degree N] then 500m [N38 degree W] then 300m [W29degree S] and finnally 400m [S13degree E] Homework Equations find this resultant displacement. The Attempt at a Solution my problem is .. [E47 degree N] ... does that mean i must put the...
  19. D

    How Do Ships A and B Move Relative to Each Other?

    Two ships, A and B, leave port at the same time. Ship A travels northwest at 19 knots and ship B travels at 28 knots in a direction 40° west of south. (1 knot = 1 nautical mile per hour; see Appendix D.) (a) What is the magnitude the velocity of ship A relative to B? 35.181 knots (b) What...
  20. B

    Problem with relative motion in two dimensions

    Homework Statement Ship A is located 4.8 km north and 3.0 km east of ship B. Ship A has a velocity of 22 km/h toward the south and ship B has a velocity of 40 km/h in a direction 37° north of east. (a) What is the velocity of A relative to B (Express your answer in terms of the unit vectors i...
  21. R

    Relative motion with cart and ball

    Homework Statement A cart moves with velocity vC = 10 m/s in the horizontal direction as shown below. [PLAIN]https://online-s.physics.uiuc.edu/cgi/courses/shell/common/showme.pl?courses/phys100/fall10/hwb/04/01/cart.gif A ball is ejected from the cart with an initial velocity vB...
  22. A

    RELATIVE MOTION wooden boxcar, sniper, bullets oh my

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  23. I

    Can the problem about relative motion be solved without using calculus?

    I have posted the problem and and the solution of part a,b,c in file 1.doc. This is problem from ch. 4 of serway. It doesn't yet assume calculus. I have question about the part c. I did it using calculus. but the book's solution uses the kind of arguments which i am not able to understand. Is...
  24. JJBladester

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  25. JJBladester

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  26. E

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  27. M

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    I'm watching a lecture video describing the following situation: There is a red ball and a green ball on a collision course. The green ball moves with a constant velocity 6 m/s due East, while the red ball moves with a constant velocity 2 m/s due west. They are saying that the velocity of...
  28. P

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  29. P

    Calculating Radial Acceleration in Olympic Hammer Throw

    Homework Statement confession Olympic hammer competition, competitor turns mass 7.3 kg ball at the end of a metal cable length 1.2 meters. Throw the hammer was released some 1.3 meters high 21 ° angle above horizon. Last horizontal distance was 83 m hammer, what is the radial acceleration of...
  30. I

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    This is not homework. I am reviewing all of the calculus that I have forgotten. Howard Anton's Calculus w/Analytical Geometry, 5th ed., section 4.1, prob #32: A police helicopter is flying due north at 100km/hr and at a constant altitude of 1/2mi. Below, a car is traveling west on a...
  31. J

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    Homework Statement Two ships, one moving 15 degree west of north with a speed 25 mi/h., the second moving 25 degree south of west with a speed 20 mi/h. relative to water pass each other. Find the velocity of the second ship relative to the first ship (magnitude and direction). Homework...
  32. O

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    Homework Statement An escalator is 20.0m long. If a person stands on the escalator, it takes 50.0s to ride from bottom to the top. a) if a person walks up the moving escalator with a speed of 0.500 m/s relative to the escalator how long does it take for the person to get to the top...
  33. E

    Football Throw - Could be Relative Motion?

    Homework Statement Quarterback Fred is going to throw a pass to tight end Doug. Doug is 20 m in front of Fred and running straight away at 6.0 m/s when Fred throws the 500 g football at a 40 angle. Doug catches the ball without having to alter his speed and runs for the game-winning pass...
  34. M

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  35. M

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    1. A cameraman on a pickup truck is traveling westward at 19 km/h while he videotapes a cheetah that is moving westward 38 km/h faster than the truck. Suddenly, the cheetah stops, turns, and then run at 50 km/h eastward, as measured by a suddenly nervous crew member who stands alongside the...
  36. I

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    Please help. I am starting to think the answer in the back of my book is wrong. Refer to picture below. Question: Find the speed of the elevator if the winches A and B both pull the rope at 5 m/s. Answer is 2.14m/s. How? I have no idea. I am not the kind to just give up. Thank you...
  37. G

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    Homework Statement Two arrows are fired straight up. The first is at 40 m/s and the second at 60 m/s and 3 seconds after arrow one. At what hieght will the arrows meet in the air. Homework Equations ? s=ut+1/2 at^2 The Attempt at a Solution s1=s2 t2=t1+3...
  38. P

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    Homework Statement A passenger walks from one side of a ferry to the other as it approaches a dock. If the passenger's velocity is 1.90 m/s due north relative to the ferry, and 4.5 m/s at an angle of 33.0° west of north relative to the water, what are the direction and magnitude of the ferry's...
  39. E

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    So, for example, 2 objects are moving towards each other. There is a frame where 2 object move with (for the sake of simplicity thy both move with the same velocity) the velocity V Then there is a frame where one of the object stand still, but the other moves towards it with the velocity 2V...
  40. R

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    Homework Statement The navigator of an airplane plans a flight from one airport to another 1200km away, in a direction 30 degrees east of north. The weather office informs him of a prevailing wind from the west, of 80km/h. The pilot wants to maintain an air speed of 300km/h. What heading...
  41. TurtleMeister

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    I've been reading the threads in this forum about relative motion and time dilation and I would like to know if I am understanding things correctly. The atomic clocks aboard the GPS satellites are programmed with a "factory offset" (according to Wikipedia) of +7us/day for relative motion and...
  42. C

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    Homework Statement http://www.lboro.ac.uk/faculty/eng/engtlsc/Eng_Mech/pastpapers/exam2001.pdf Problem B6 Collar A slides along a horizontal rod that is rotating as shown in Figure Q.B6 with an angular velocity of 5 rad/s in the anti-clockwise direction. At a distance of 200 mm from the...
  43. A

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    Homework Statement http://www.hdimage.org/images/bgkkpt63ckx96gu3xgh.jpg Homework Equations aA = aA/B + aB VA = VA/B + VB The Attempt at a Solution After staring at this question for some time, I finally had a go and got an answer of 1.25 rad/s, which is incorrect. I am totally...
  44. A

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    Homework Statement http://www.hdimage.org/images/n5gdv4yrqp0wkl11ioae.jpg Homework Equations aA = aB + aA/B The Attempt at a Solution I have made a few attempts at this one, and I have gotten absolutely no where. All I have figured out is that the edge of the smaller circle will be...
  45. H

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    Homework Statement An airplane maintains a heading due west at an air speed of 900km/h. it is flying through a hurricane with winds of 300km/h, from the northeast. a.in which direction is the plane movie relative to the ground b.what is the planes ground speed? c. how long would it take the...
  46. S

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  47. U

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    Before I start studying the relativity theories, I have to grasp this concept: Suppose two cars are moving with constant velocities in any direction and a ball is thrown straight up and comes back straight down. This will happen in both cars. But what if a person in one car observes the...
  48. J

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    Homework Statement 1. A boat takes 3 hours to travel 30 km down a river, then 5 hours to return. How fast is the river flowing? 2. Taking a moving sidewalk, without walking, takes 75 seconds to arrive at baggage claim. Walking, not on the moving sidewalk, takes 50 seconds. How long...
  49. M

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    Homework Statement A bolt drops from the ceiling of a train car that is accelerating northward at a rate of 3.50 m/s2. (a) What is the acceleration of the bolt relative to the train car? (b) What is the acceleration of the bolt relative to the Earth? The Attempt at a Solution (a)10.4...
  50. R

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    I don't understand the physical meaning of one of my dimensions/variables. Let there be a gravitational potential \phi (x_a), a=1,2,3. Equation of motions of a freely falling particle is: \frac{d^2 x_a}{d t} = - \frac{\partial \phi}{\partial x_a}. If there are 2 particles falling, family of...
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