What is Relative velocity: Definition and 413 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. R

    Swimmer and River (Relative Velocity)

    Homework Statement A swimmer is to reach at a point 30 degree upstream on the other side of a river flowing with velocity 5 m/s. The velocity of the swimmer w.r.t. water is 5\sqrt{3}. The swimmer should steer at an angle?? The Attempt at a Solution I am unable to guess the scenario...
  2. S

    Frequency shift and relative velocity

    Suppose two observers A and B are moving with regard to each other at relative velocity = v = 0.5c, which they have determined for each other by measuring the time interval that a point of the other frame takes to pass by two points of their own frame, whose clocks are synchronized using the...
  3. G

    Relative Velocity Homework: Find Speed of River

    Homework Statement A tugboat releases a barge and continues down the river for t = 64 min. Then it returns and finds the barge 3.9 km downstream from its initial position. Assuming that the speed of the tugboat was constant with respect to the water, the speed of the river is (in km/h)...
  4. V

    Relative Velocity of a Helicopter

    Homework Statement Average Wind Velocity 38km/h [25 degrees N of E] Helicopter needs to achieve 91km/h [17 degrees W of N] Homework Equations r=sqrt(x^2+y^2) The Attempt at a Solution y=38sin25 + 91sin98 = 106.17 x=38cos25 - 91cos98 = 47.1 r= 116.15 answer should be 94km/h
  5. F

    Calculating Relative Velocity: Plane and Wind Speeds | Homework Help

    Homework Statement An airplane is heading due south at a speed of 620 km/h. If a wind begins blowing from the southwest at a speed of 80 km/h (average), calculate the following. (a) the velocity (magnitude and direction) of the plane relative to the ground (566.27) km/h (5.733)°...
  6. M

    Relative velocity - two cars

    Homework Statement how long does it take a car traveling in the left lane at 60 km/h to overtake another car traveling in the right lane at 40 kn/h when the cars front bumpers are initially 100 m apart? Homework Equations relative velocity equations V ab = v ae + V be The Attempt...
  7. S

    How to calculate relative velocity in SR

    I assume that, in SR, both observers moving relative to each other calculate the same relative velocity (v). But I wonder how. If they use clocks and rods, I see two possible methods: (a) combination of the measurements of two frames and (b) only "home-made" measurements. In method (a), Mr A...
  8. C

    How Does Relative Velocity Affect a Swimmer's Path Across a River?

    A swimmer heads directly across a river, swimming at 1.6m/s relative to the water. She arrives at a point 40m downstream from the point directly across the river, which is 80m wide. A) What is the speed of the river current? B)What is the swimmer's speed relative to the shore? C)In what...
  9. M

    Relative velocity of rain to car

    Homework Statement Hi, I've been trying to do this problem with limited success. If someone could help me realize where I went wrong, I would greatly appreciate it Assume the downward direction is positive. A car travels due east with a horizontal speed of 53.7 km/hr. Rain is falling...
  10. A

    Relative Velocity Homework: Solve for Ball Rise Height

    Homework Statement A science student is riding on a flatcar of a train traveling along a straight horizontal tract at a constant speed of 10.0m/s. The student throws a ball along a path that she judges to make an initial angle of 60.0degrees with the horizontal and to be in line with the...
  11. A

    Calculating Relative Velocity of Grenade in Moving Vehicles

    Homework Statement In an action-adventure film, the hero is supposed to throw a grenade from his car, which is going 91.0 km/h, to his enemy's car, which is going 106 km/h. The enemy's car is 14.5 m in front of the hero's when he let's go of the grenade. a)If the hero throws the grenade so...
  12. T

    Relative Velocity (Two-Demensional Motion and Vectors)-hw help

    Homework Statement George V Coast in Antartica is the windiest place on earth. Wind speeds there can reach 300 km/h. If a reasearch plane flies against the wind with a speed of 450 km/h relative to the wind, how long does it take the plane to fly between two reasearch stations that are 250 km...
  13. K

    Relative Velocity and Projectile Motion

    Homework Statement A low-flying helicopter flying a constant 215 km/h horizontally wants to drop secret documents to his contact's open car which is traveling 155 km/h on a level highway 78.0 m below. At what angle (to the horizontal) should the car be in his sights when the packet is...
  14. E

    Relative Velocity: Can We Exceed the Speed of Light?

    What is our relative velocity with respect to the largest mass in the universe? Can this velocity exceed the speed of light, as the force accelerating us is strictly gravitational? If it's possible, wouldn't us, traveling at or faster than c, be a better reason for why only a fraction of...
  15. C

    Relative Velocity of a pickup truck

    Homework Statement A person riding in the back of a pickup truck traveling at 70 km/h on a straight, level road throws a ball with a speed of 15 km/h relative to the truck in the direction opposite to the truck's motion. What is the velociy of the ball (a) relative to a stationary observer by...
  16. B

    How Do Wind Velocity and Direction Affect Aircraft Travel Time and Direction?

    Homework Statement An aircraft is to fly from a from point A to an airfield B 600km due North of A. If a stead wind of 90 km/hr is blowing from the north-west, find the direction of the plane should be pointing and the time to reach B if the cruising speed of the aircraft in still air is 200...
  17. S

    How Do Canoeists' Velocities Reveal Water Speed and Their Effort?

    Ok, I can not get the answer to this question! Two canoeists in identical canoes exert the same effort paddling and hence maintain the same speed relative to the water. One paddles directly upstream (and moves upstream), whereas the other paddles directly downstream. With downstream as the...
  18. H

    Relative Velocity: Henrik's Understanding

    Hi. Movement is relative I understand. Whether atom A passes atom B in empty space or B passes A is only a question of viewpoint. One can only be moving or still compared to something else. Somewhere at the edge of the visible universe everything is moving away from me with almost the speed...
  19. O

    Relative velocity and Michelson Morley experiment

    Homework Statement I was reading up on an experiment,The Michelson Morley experiment, in preparation for Physics lab. Then there was this problem. The textbook stated that the velocity of the light ray that was traveling perpendicularly to the ether wind was \root{c^2-v^2}. Shouldn't it have...
  20. S

    Find David's Velocity w/ Respect to John: Relative Velocity Homework

    Homework Statement John equation of motion is Rj(t)=(t^2+3t)i + tj. David's equation of motion is Rd(t)=5ti+t^3j. At t=1 find David's velocity with respect to john. Homework Equations The Attempt at a Solution I know if you plug in the one that will give you the position they are...
  21. N

    High School relative Velocity question

    Relative Velocity & Vectors I have the below question for Summer Physics (basically just taking physics over the summer instead of during the year) I completed part A by doing Y-component for mee eun is 15sin30 and x-component is 15cos30. For Lokesh I got 20sin50 for the y and 20cos50 for...
  22. Z

    How to Calculate Relative Velocity in Wind for a Plane and Cyclist?

    a,The Speed Of an aircraft in still air is 300 km/h. In a wind of speed 140 km/h, blowing from a bearing of 230, the aircraft flies due east. Find i, the course set by the pilot ii, the time taken for the aircraft to travel 100 km. b,To a cyclist traveling due east at 18 km/h the wind...
  23. M

    How Do You Calculate Angular Velocity in a Rolling Wheel Problem?

    Homework Statement http: // i110.photobucket .com/albums/n104/juanmedina/sombreroface1.jpg (to see the picture of the problem deleted the spaces in the link provide above. I'm not allowed to post pics because I don't have 15 post the wheel shown rolls without slipping on the horizontal...
  24. A

    Calculating the Speed of a River Current Using Relative Velocity

    Homework Statement I have a boat trying to cross a river with a current flowing -> The boat is attempting to make it straight across (90d). In order to do this I have to change the volocity to 119.38 and the angle to 100.3. So what is the speed of the current? Homework Equations...
  25. C

    Why Should a Boat Row at 90 Degrees to Cross a River Fastest?

    Hi! I'm having trouble with some relative velocity problems. Example A) A boy wishes to row across a river in the shortest possible time. He can row at 2 m/s in still water and the river is flowing at 1 m/s. At which angle (theta) should he point the bow (front) of his boat. I tried to set up...
  26. A

    How Do You Calculate a Boat's Relative Velocity with a Current Using Cosine Law?

    Homework Statement 2. A boat heads 15° west of north witha water speed of 3m/s. Determine its velocity relative to the ground when there is a 2m/s current from 40° east of north. Homework Equations cosine law The Attempt at a Solution I found the angle between the two...
  27. M

    Does the Earth's spin impact time dilation for satellites and GPS receivers?

    Is it plausable to take into account the speed of the Earth's spin when calculating tmie dilation for satellites and GPS receivers? You could take into account the satellites spining against the Earth's orbit, with the Earth's orbit and at an angle? I put it into my project but is it a...
  28. N

    Relative velocity of third object

    With reference to the sketch attached, if A and B is having a relative velocity of 0.9c,and B and C having a relative velocity 0.9c What will be the relative velocity between A and C? (all in x direction)
  29. manjuvenamma

    Is the Book's Answer to the Relative Velocity Problem Incorrect?

    I raised this question in the courseware section and I got only one response. To improve the response, I am repeating the question here. Please see it. I got one answer and the book at the receprocal of my answer. This is not just for this problem for several problems of this nature the...
  30. manjuvenamma

    What Is the Correct Angle for an Umbrella in Rain Relative to a Walking Man?

    Homework Statement Rain is falling down vertically. To a man walking on the road, velocity of rain appears to be 1.5 times his velocity. Then to protect himself from rain, he holds his umbrella at an angle (theta) to the vertical such that tan (theta) = Homework Equations The...
  31. C

    Relative velocity of two speeding cars

    Homework Statement Given the following conditions, what is the relative velocity of 2 cars if their ground speeds are 80km/h for Car A and 45 km/h for Car B? a) both cars are heading in the same direction, A behind B in the reference frame of A b) Use the reference frame of B for part A) c)...
  32. D

    Helicopter Speed Relative to Ground: Solve w/ Vector Components

    Homework Statement A helicopter's velocity relative to the air is 55m/s[W35^\circN] The wind speed is 21 m/s[E]. I need to find the speed of the airplane relative to the ground. Homework Equations The Attempt at a Solution I tried using vector components for this equation. Since the vertical...
  33. G

    How Should a Plane Adjust Its Course in Crosswinds to Fly Due North?

    A plane is flying at a speed of 206 km/h in still air. There is a wind blowing at a speed of 76.6 km/h at 48.7 degrees to the east of north, and the pilot wishes to fly due north. What angle should the plane fly? (assume the angle is measured between the plane and north.) What speed does the...
  34. Z

    Solve for Speedboat Direction: Coast Guard Cutter Intercepts Unidentified Ship

    Homework Statement A Coast Guard cutter detects an unidentified ship at a distance of 23.1 km in the direction 16.8° east of north. The ship is traveling at 24.7 km/h on a course at 43.1° east of north. The Coast Guard wishes to send a speedboat to intercept the vessel and investigate it. If...
  35. D

    Relative Velocity & De Broglie's Theory

    Hello, I would like to determine the Wavelength of many different macroscopic objects for a theoretical project and I am having trouble understanding how to use the equation correctly due to relative velocities. When computing Wavelength = h/ Velocity * Mass I see example of calculating...
  36. S

    Relative Velocity Swimmer Problem

    Homework Statement A swimmer maintains a speed of 0.15 m/s relative to the water when swimming directly toward the opposite shore of a straight river with a current that flows at 0.75 m/s. (a) How far downstream is the swimmer carried in 1.5 minutes? (b) What is the velocity of the...
  37. T

    Relative Velocity coordinate system

    (a) A point is observed to have velocity v_A relative to coordinate system A . What is its velocity to coordinate system B which is displaced from system A by distance R ? ( R can change in time) I think its v_B = v_A - \frac{dR}{dt} . But I am not completely sure why this is the...
  38. P

    Relative Velocity: Al & Bob's Trip to Ted's Place

    Two swimmers, Al and Bob, live on opposite shores of a 200.0 m wide river that flows east at 0.70 m/s. Al lives on the north shore and Bob lives on the south shore. They both set out to visit a mutual friend, Ted, who lives on the north shore at a point 100.0 m upstream from Al and 100.0 m...
  39. S

    Relative Velocity problem - stuck, lacking ideas.

    Homework Statement Halliday/Resnick/Walker, 1 - Mechanics, 7th Edition. Chap. 4, Exercise 57 - Relative Movement in One Dimension (I'm sorry if translation sounds confusing at first, the book is in Portuguese) A suspicious man runs as fast as he can on a conveyor belt, taking aprox. 2.5...
  40. M

    How does relative velocity affect the time it takes for two objects to meet?

    Homework Statement 1.How long, in seconds, does it take an automobile traveling 50.0 km/h to become even with a car that is traveling in another lane at 40.0 km/h if the cars' front bumpers are initially 124 m apart? 2.A shopper in a department store can walk up a stationary (stalled)...
  41. P

    How Do You Calculate Relative Speed of Particles Moving Orthogonally in Physics?

    I'm having trouble picturing the following problem. In a given inertial frame, two particles are shot out simultaneously from a given point, with equal speed u, in orthogonal directions. a) Without using 4-vectors show that the speed of each particle relative to the other is given by...
  42. C

    Relative Velocity of an aircraft carrier

    Homework Statement The Attempt at a Solution Vch = Vce + Vhe Do I have this correct? I am guessing I need to find the velocity of the carrier with the respect to earth, and also find the velocity of the helicopter with respect to earth. Than with these two answers I can find...
  43. C

    How Does Throwing a Ball from a Moving Truck Affect Its Velocity to an Observer?

    Homework Statement A student is riding in the back of a truck traveling along a straight level road at Vt = 20 m/s. He faces toward the rear of the truck and throws a ball with a velocity of 15 m/s at an angle of 37 degrees above the horizontal relative to the truck. He releases the ball 2.0...
  44. S

    How Does a 45 Degree Angle Affect Boat Navigation in a River Current?

    1. A boat, whose speed in still water is 2.20m/s, must cross a 260m wide river and arrive at a point 110m upstream from where it starts. To do so, the pilot must head the boat at a 45 degree upstream angle. What's the speed of the river's current? 2. How do you incoporate 45 degrees into the...
  45. E

    Calculating Flight Time for Birds in Windy Conditions

    Canadian geese migrate essentially along a north-south direction for well over a thousand kilometers in some cases, traveling at speeds up to about 100 km/h . If one such bird is flying at 100 km/h relative to the air, but there is a 42.0 km/h wind blowing from west to east. Part A) At what...
  46. S

    Relative velocity problem. NEED HELP.

    Homework Statement A jet airliner moving initially at 300 mph due east enters a region where the wind is blowing at 100 miph in a direction 30° north of east. What is the new velocity of the aircraft relative to the ground? Homework Equations I don't know any equations for this question...
  47. M

    What is the relative velocity of two cars traveling in the same direction?

    Homework Statement Two cars, A and B, are traveling in the same direction, although car A is 186m behind car B. The speed of A is 24.4m/s, and the speed of B is 18.6m/s. how much time does it take for A to catch B? Homework Equations Va+Vb=Vab, x=1/2(V0x+Vx)t The Attempt at a...
  48. C

    Help with an airplane problem (relative velocity)

    Homework Statement An airplane pilot sets a compass course due west and maintains an airspeed of 218 km/hr. After flying for a time of 0.510 hr, she finds herself over a town a distance 124km west and a distance 16 km south of her starting point. Find the magnitude of the wind velocity (in...
  49. J

    Relative Velocity of two swimmers

    Homework Statement Two swimmers, Alan and Beth, start together at the same point on the bank of a wide stream that flows with a speed v. Both move at the same speed c (c > v), relative to the water. Alan swims downstream a distance L and then upstream the same distance. Beth swims so...
  50. C

    Dynamics Problem, Relative velocity of rigid body in planar motion

    http://wps.prenhall.com/wps/media/objects/3076/3149958/studypak/questions/html/Ch16/9e_16_43.html That is the image of the problem, which includes a solution. PROBLEM- Besides being really confused on their work, the solution they give and the solution in the back of my book are both...
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