Relative motion Definition and 282 Threads

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. U

    Relative Motion of a Motorcyclist on a Rotating Bike

    Homework Statement A motorcyclist accelerates rapidly so the bike entirely rests on the back wheel, while the midpoint of the back wheel O' accelerates with constant acceleration a_o' horizontally. The entire bike rotatoes with angular velocity \frac{d}{dt} \theta and angular acceleration...
  2. NATURE.M

    Will the Ice Cream Land on Your Professor's Head? Exploring Relative Motion

    Homework Statement You are at the mall on the top step of a down escalator when you lean over laterally to see your 1.80 m tall physics professor on the bottom step of the adjacent up escalator. Unfortunately, the ice cream you hold in your hand falls out of its cone as you lean. The two...
  3. H

    Relative Motion - Airplane Problem

    Homework Statement An airplane has a velocity 325km/h relative to the air. It is going in a direction [S30W]. There is a wind velocity of 80km/h[W]. What is the velocity of the plane relative to the ground? Homework Equations aVg + pVa = pVg (velocity of air relative to ground +...
  4. J

    Vector / Relative Motion Problem

    Homework Statement A pilot flying East from Hartford to Providence (distance of 50 miles) releases a balloon directly over Providence. 15 minutes later, the pilot turns around. The pilot sees the balloon again over Hartford. What is the approximate wind velocity? (Assume constant airspeed...
  5. S

    Solve 1D Relative Motion Homework: Ball Thrown, Elevator, Tennis & Baseballs

    Homework Statement 1)A ball is dropped from the top of a 56.0 m-tall building. After 2.00 s, another ball is thrown upward from the ground. When the two balls pass the same point, they have the same speed. How fast was the upward-bound ball thrown? 2)You are riding an elevator with an...
  6. S

    One Dimentional Relative Motion

    Homework Statement An ocean liner approaches a peer at 20km/h. When the ocean liner is 10 km away, the captain sends a speedboat to the pier to pick up the harbour pilot, who will help dock the ocean liner. The speedboat takes 12 min to get to the pier. a) How long would the speedboat take to...
  7. M

    Reference frame in relative motion

    I red a classical mechanics concept in a book. Imagine that we have two observers with two frames of reference F1 and F2 observing a particle P in motion. One of the observer is in motion and another is at rest,(lets take F1 is at rest and F2 is in translation motion with velocity V) let r1 be...
  8. C

    Dynamics - relative motion, planes Q

    Homework Statement Aircraft A is describing a circular flight path in an anti-clockwise direction at 125km/h Aircraft B is flying the same path but in the opposite direction at 225km/h. If the radius of the flight path is 5km, calculate the acceleration of A relative to B when Aircraft A is...
  9. J

    Confused by Relative Motion? Get Answers Here!

    Disclaimer: This is not for any class. I have downloaded this book ( http://www.ck12.org/book/CK-12-Physics---Intermediate/ ) and am ( attempting to (: ) work through it on my own. I am going through the section on relative motion ( section 3.3 in the book ) and am confused by a portion. It...
  10. A

    Using relative motion (2D) to get rain speed & direction when running

    Homework Statement A person moving towards east with a speed 'v' observes the rain to be falling vertically downwards. When he doubles his speed, the rain appears to come at 30° angle with the vertical. Find the actual speed and direction of rain with vertical. Homework Equations...
  11. V

    Is relative motion different from acceleration?

    I saw someone post a question or a comment about relative motion and acceleration. It got me thinking about the spaceship in deep space with rocket boosters. Well, when that guy or girl hits the booster, he or she accelerates, but the person is not necassarily moving relative to anything. Is...
  12. S

    Question about relative motion: 3 Golden Retrievers in deep space

    Gravitational effects from large bodies of mass are nonexistent. These golden retrievers are in deep, deep space. They are named Mr. Squabbles, Alfredo, and Billy. Mr. Squabbles is suspended in space (at rest)--he has not been acted upon by any force. (If that's possible.) Alfredo has a...
  13. M

    What direction will a man appear to be rowing in relative motion?

    Hello, If a man how is able to row on still water at 2.5m/s. If the water is moving at 1.5m/s, in which direction should he row. The answer is he should row at 53.1 degrees upstream but the question for an observer on the boat and another observer on land, how will the motion appear? For an...
  14. R

    Relative Motion- Airplane/Wind

    Homework Statement A jetliner has a cruising air speed of 620mph relative to the air. Part B How long does it take this plane to fly round-trip from San Francisco to Chicago, an east–west flight of 2000 miles each way, if the wind is blowing at 120mph from the west to the east? Homework...
  15. P

    Simple problem about relative motion.

    Homework Statement A body consisting of two spheres attached by a 10 meter solid long rod is rolling down a 45 degree incline at one end while rolling up a 45 degree incline on the other end. At the instant when the connecting rod is horizontal the sphere rolling down has the velocity 2 m/s...
  16. A

    What is your velocity when walking on a moving train in the opposite direction?

    You are on a train traveling east at speed of 14.0 m/s with respect to the ground. if you walk west toward the back of the train, with a speed of 1.4 m/s with respect to the train, what is your velocity with respect to the ground? I got the answer as 12.6 m/s east but is my answer going to...
  17. Q

    What Is the Velocity of a Ladybug on a Moving Chair Relative to the Ground?

    Homework Statement A ladybug with a velocity of 10.0mm/s [W] crawls on a chair that is being pulled [50deg N of W] at 40.0mm/s. What is the velocity of the ladybug, relative to the ground?Homework Equations pythag theorum component vectors sohcahtoa The Attempt at a Solution Let [N] and [W]...
  18. S

    How Does Moving at 20sqrt(2) m/s Affect the Projectile's Trajectory Equation?

    Homework Statement To an observer not in motion in the ground, the trajectory of a projectile is described by: y = x - 10^{-3}x^2(In SI units) Where it was adopted x = 0 and y = 0 for the origin point. Determine the trajectory equation for an observer that moves at 20sqrt(2) m/s in relation to...
  19. L

    Physics - Relative Motion Homework Help

    Homework Statement A ferryboat, whose speed in still water is 4.00m/s, must cross a river whose current is 3.00m/s. The river runs from west to east and is 128m wide. The boat is pointed north. a) If the boat does not compensate for the flow of the river water and allows itself to be...
  20. P

    Two dimensional relative motion; boat and river problem

    Homework Statement Mary needs to row her boat across a 100-m-wide river that is flowing to the east at a speed of 1.0 m/s. Mary can row with a speed of 2.0 m/s. a) If Mary points her boat due north, how far from her intended landing spot will she be when she reaches the opposite shore? b)...
  21. P

    Question about pulley with relative motion

    for part(i) the answer is g/4 + g/2 = 3g/4 ms^-2 how to calculate the acceleration of the 9N blcok relative to the small pulley to be g/4?? Did I miss something? thank you so much!o:)
  22. C

    Relative motion of train and platform observer

    Homework Statement A train is passing a platform at 0.75c, and an observer, stationary and at the middle of the platform, sees two bolts of lightning simultaneously hit the front and back of the train when the train's middle was adjacent to the middle of the platform. A passenger on the train...
  23. P

    How Far Will You Travel Before Hitting the Mosquito?

    Homework Statement A mosquito flies toward you with a velocity of 2.2 km/h (E). If you are traveling toward the mosquito with a speed of 1.9 m/s, and a distance of 21.0 m separates you and the mosquito initially: A) What will your displacement be when you hit the mosquito? (7) B) How long...
  24. D

    Relative Motion problem that doesn't have right triangle relationship

    Homework Statement a) Find the speed of the boat with respect to the Earth. (km/h) b) Find the speed of the boat with respect to the river if the boat's heading in the water is 60° south east (km/h) Homework Equations v(x) = v cos(θ) v(y) = v sin(θ) v = √(vx^2+vy^2) but can't use it in...
  25. T

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  26. X

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    1) In the following four scenarios, determine the sign of the ball’s velocity and acceleration. Up is positive. The ball is thrown straight up. (Velocity is positive, Acceleration is negative) Up is positive. The ball is dropped straight down. (Velocity is negative, Acceleration is negative)...
  27. S

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  28. coktail

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  29. J

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    a motorboat moving at 8km/h relative to the water travels from A to a point B 10km whose bearing from A is 150. it then travels to C,10km from B and due west of B. if there is a current of constant speed 4km/h from north to south,find the 2 courses to be set. having a bit of trouble with...
  30. I

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    My understanding of relativity is that if two masses are in constant motion relative to each other, either one of them could be considered at rest with the other moving and it makes no difference which. However thinking about a collision between a big truck and a small car makes me wonder about...
  31. S

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  32. S

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  33. C

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  34. A

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    Please help me with the following problem... velocity of man wrt to ground is 3km/h due east. velocity of rain with respect to man is 4km/h and falls vertically downwards. If the man moves at 6km/hr then the velocity of rain wrt to man is?
  35. T

    Doppler effect and relative motion

    Hello everyone! I need some help with a Doppler effect/relative motion question. Homework Statement A whistle with a frequency of 1200 Hz is traveling south at a velocity of 30.0 m/s. You are traveling north away from the whistle at a speed if 18.0 m/s. If the speed of sound is 340 m/s, what...
  36. T

    Simple Mechanics, relative motion example

    Homework Statement Might be the sketch most useful first: The prism is sliding horizontally from left to right under condition : S(t)=4*t*t+5*t+1[cm] and the bar OA is rotating, point A is sliding over the prism's slope and point O is the immobilized center of bar's rotation, OA=10cm...
  37. S

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    Imagine an Aeroplane held above the Earth's surface for 12 hours, having no contact with the surface of the earth. Suppose that the initial location at time t=0 is Asian continent. So after t = 12 hours, can we expect the aeroplane to be in some other continent or will it be in the same location.
  38. R

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    Homework Statement While driving north at 25 during a rainstorm you notice that the rain makes an angle of 38 with the vertical. While driving back home moments later at the same speed but in the opposite direction, you see that the rain is falling straight down. a)From these observations...
  39. A

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    A river flows east to west at 3.0 m/s and is 80 m wide. A boat, capable of moving at 4.0 m/s, crosses in two different ways. (a) Find the time to cross if the boat is pointed directly north and moves at an angle downstream. (b) Find the time to cross if the boat is pointed at an angle upstream
  40. C

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    I understand the concepts behind SR and Lorentz transformations and was explaining the basics to my son by illustrating the classic laser-beam-in-a-train-car explanation. But then I started thinking... If I was in a boxcar w/ a clear wall and was throwing a ball straight up, measuring the time...
  41. C

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    Not sure if this belongs in the SR forum, but here goes. I understand the concepts behind SR and Lorentz transformations and was explaining the the basics to my son by illustrating the classic laser-beam-in-a-train-car explanation. But then I started thinking... If I was in a boxcar w/ a...
  42. U

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    Homework Statement http://imgur.com/EcjIaHomework Equations I already got the first part (v_b/a) i need to find r dot and theta dotThe Attempt at a Solution well i got v_b/a. for r I was thinking of using sqrt(y^2 +x^2) at the r and taking derivatives of that. i don't quite understand polar...
  43. N

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    Homework Statement 1) A boy is floating on a raft in a river. THe water flows at a speed of 12m/s east. The boy's feet kick the water,causing a velocity of 2m/s at an angle of 43 degrees north of east. Using Vector components, calculate the magnitude of the raft's velocity. 2)One vector...
  44. D

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  45. B

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    A swimmer crossing a river proceeds at an absolute speed of 2.5 m/s on a course oriented at a 45degree angle to the 1 m/s current. Given that the absolute velocity of the swimmer is equal to the vector sum of the velocity of the current and the velocity of the swimmer with respect to the current...
  46. S

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    Homework Statement A blimp is ascending at the rate of 7.6 m/s at a height of 67 m above the ground when a package is thrown from its cockpit horizontally with a speed of 4.5 m/s. (a) How long does it take for the package to reach the ground?(b) With what velocity (magnitude and direction)...
  47. F

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    Ship A is located at 4 km north and 2.5 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 degrees north of east. (a) What is the velocity of A relative to B in unit-vector notation with i toward the east? (b) Write an...
  48. C

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    Im reading a page out of Griffiths about 2 guys holding a wire loop on a railroad car and then traveling through a B field on the track. As the guys travel at a speed v through the B field the electrons will start to move in the conductor. If we view it from the point of the the B field...
  49. L

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    Homework Statement I figured I'll try this again. A battleship steams due east at 24 km/h. A submarine 4.0 km away fires a torpedo that has a speed of 50 km/h. If the ship is seen 20º east of north, in what direction should the torpedo be fired to hit the ship? Homework Equations...
  50. L

    Having trouble with relative motion

    Homework Statement A battleship steams due east at 24 km/h. A submarine 4.0 km away fires a torpedo that has a speed of 50 km/h. If the ship is seen 20º east of north, in what direction should the torpedo be fired to hit the ship? Homework Equations x motion of ship: x = vt x...
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