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. J

    Relative Motion of River in Two Dimensions

    A 340-m-wide river has a uniform flow speed of 0.84 m/s through a jungle and toward the east. An explorer wishes to leave a small clearing on the south bank and cross the river in a powerboat that moves at a constant speed of 3.8 m/s with respect to the water. There is a clearing on the north...
  2. B

    Calculating Boat Speed in 2-D Relative Motion

    Suppose the river is moving east at 4.80 km/h and the boat is traveling Theta = 43.0° south of east with respect to the Earth. You will have to solve two equations and 2 unknowns. (a) Find the speed of the boat with respect to the Earth. kh/m (b) Find the speed of the boat with respect...
  3. S

    Question on relative motion and circular motion.

    Hey guys, I've been working on this physics for a few hours, and feel like I am just missing a key point. At first I felt that the problem was missing data, until in the same section I found another that I felt the same. Now I feel like I'm missing a concept or two. The first problem I have...
  4. A

    Relative motion: Understanding acceleration and velocity in an elevator

    If an elevator moves at an acceleration of 5 ft per second squared going up and when the velocity is 8 ft/sec going up, a screw falls from the ceiling of the elevator down to the floor of the elevator. The height of the elevator is 9 ft. Find the length the screw dropped. My problem: length=...
  5. F

    Relative Motion. Wheel and axle.

    This is the PROBLEM: Flinstone has a problem too. He built a beam mover, described below (on the attachment, DOC file, look down), but can't figure it out. Perhaps you can help. Two identical wheels and axles sets were carved from from logs. In each set, the 50 cm diameter wheels and the 14...
  6. F

    Having trouble with a relative motion problem

    Two ships, A and B, leave port at the same time. Ship A travels northwest at 20 knots and ship B travels at 27 knots in a direction 43° west of south. (1 knot = 1 nautical mile per hour; see Appendix D.) What are (a) the magnitude (in knots) and (b) direction (measured relative to east) of the...
  7. D

    Paper boy problem (relative motion)

    a newspaper boy throws newspapers sideways onto the porches of his customers while riding his bicycle along the sidewalk. the sidewalk is 15 m in from of the porches. the boy throws the papers at a horizontal speed of 6 m/s relative to himself and rides the bicycle at 4 m/s relative to the...
  8. S

    Relative motion/ Vector Question

    Please..give It A Try "Ship A is located 4 km north and 2.5 km east of ship B. Ship A has a velocity of 22km/h towards the south and ship B has a velociy of 40 km/h in a direction of 37(degrees) north of east. A)what is the velocity of A relative to B B)write an expression for the position...
  9. F

    Relative motion question again

    I really need help with this question A swimmer who achieves a speed of 0.75 m/s in still water swims directly across a river 72 m wide. The swimmer lands on the far shore at a position 54 m down stream from the starting point. a)Determine the speed of the river current. b)Determine the...
  10. F

    Helicopter Velocity in Relation to Ground with Wind

    I really need help with these questions they are too hard. Anyways the question is: A helicopter travels with an air speed of 55 m/s. The helicopter heads in the direction [35 degrees N of W]. What is velocity relative to the ground if the wind velocity is (a) 21 m/s [E] and (b) 21 m/s [22...
  11. 4

    Relative Motion Calculations: Solving for Time and Heading

    I spend 2 hours this evening trying to do these problems, but for these 2, I couldn't manage to even draw a proper diagram for :frown: ... For the last question, I tried to draw it, but the resultant vector wasn't matching with the answer, so obviously it was wrong...
  12. E

    Help Me Relative Motion In One Dimension.

    Help Me...Relative Motion In One Dimension. What Is the relative motion in one dimention? Drive the Acceleration equation.
  13. A

    Relative Motion and acceleration

    I tried doing this, but I can't get the exact same answer as the one given http://img246.echo.cx/my.php?image=untitled0nj.png I use relative acceleration a_a = a_b + \dot \omega \cross r + \omega \cross (\omega \cross r) + 2 \omega \cross V_{rel} + a_{rel} and as V_{rel} = 0 \dot...
  14. B

    Relative Motion problem... help! (now with scans of what I have done so far!)

    Relative Motion problem... help! (now with scans of what I have done so far!) I guess I will write the entire question out first, I am current stuck at part (e) and will provide what I believe are correct answers to the previous portions of the question: The pilot of a small plane leaves...
  15. P

    Energy in Relative Motion: Investigating a Paradox

    hello i m new to this forum n dis is my first topic i was reading about relative motion yesterday that if a train is movin with 90 km to east the observer in the train will find dat train is stationary and the Earth is moving backwards similarly for an observer on Earth train is moving n Earth...
  16. C

    How Can You Calculate the Water Current in the Elora Gorge Problem?

    Help on a Problem! Hi there everyone. I am completely lost on how to go about answering this question :cry: A sunbather, drifting down the Grand River on an inner-tube, dives off the tube as it passes under the high bridge of Elora Gorge. She swims against the current for 15 mins before...
  17. K

    Solve Relative Motion: Boat, Wood + River Flow

    Hi, I have this excercise that I've been trying to do for a couple of days now. Can anybody help me? Here's the question: A boat is moving against the direction of flow of a river and meets a piece of wood that is moving along with the river. The boat continues against the flow of the river...
  18. RadiationX

    Relative motion in 1 and 2 dimensions

    can someone explain the concept of relative motion in one and two dimensions? how do i determine relative motion?
  19. N

    Relative Motion of a football player

    A football reciever B runs the slant in pattern, making a cut at P and thereafter running with a constant speed v_B=21ft/sec at an angle of 30 degrees from the y-axis. The quarterback releases the ball with a Horizontal velocity v_A_x=100ft/sec the instant the reciever passes pont P. Determine...
  20. G

    How Do Canoeists A and B Coordinate Their Arrival Using Relative Motion?

    please help with relative motion problem! I need some help with this question, i know the axis needs to be rotated but I'm not sure how to go about doing that. I also need to know how to do it using the component method. -two canoeists, A and B, live on opposite shores of a 300m wide river...
  21. D

    Gravity and atomic fields - due to high relative motion?

    Gravity or gravitational fields are not yet understood fully. All mass bodies including the atom itself has what is called a gravitational field. Gravity is principly the partial alignment of the atomic electrical fields due to a common high velocity motion of the atoms through the universe...
  22. V

    Calculating Velocity and Direction of a Sailboat After a Sudden Gust of Wind

    A sailboat is traveling east at 5. m/s. A sudden gust of wind gives the boat an acceleration =0.80 m/s^2, 40 degree north of east 1) what is the boat's speed later when the gust subsides? 2) what is the boat's direction 6.0 s later when the gust subsides? I've a question I need to find...
  23. G

    Relative Motion in vectors form

    The question is as follow: A bird is capable of flying at 80km/h. It wishes to fly to its nest which is due East of its present position. Thre is a win blowing from the northwest at 70km/h. Find the direction relative to the air in which the bird must fly to reach its nest. I tackled the...
  24. M

    Relative Motion with Two Moving Figures: What's the Best Way?

    What is the best way to think about relative motion with two moving figures? Perhaps it depends on the problem but in general is it best to just imagine one of the figures as stopped and the other moving with its relative velocity, or could you run into some problems that way? Thanks for any...
  25. Q

    How Do You Calculate the Distance and Relative Speed Between Two Ships?

    Ships A and B leave port together. For the next two hours, ship A travels at 35.0 mph in a direction 25.0 degrees west of north while the ship B travels 80.0 degrees east of north at 30.0 mph. What is the distance between the two ships two hours after they depart? What is the speed of ship A...
  26. Q

    Calculating River Flow Using Reference Frames

    A boat takes 3.20 hours to travel 10.0 km down a river, then 6.10 hours to return. How fast is the river flowing? can someone give some suggestions as to how to do this? I am guessing you use reference frames. thanks in advance.
  27. M

    Simple Relative Motion Police Car Problem

    Ok, here’s the question: A motorist traveling at 89 km/hr is being chased by a police car at 115 km/hr. If the police car starts from 3.5 km back, how long does it take to catch the motorist? Leave time in hours. Now I’m looking at this as a relative motion problem since there is no...
  28. W

    Matter Forms Space & Time is Relative Motion

    Questions related to the Topic Title of this Thread: STM Question: "Which factor should dominate Space-Time-Matter discussions?" Time Question: "Does time exist or is it a human construct?" Matter Question: "Should mass be used in place of matter?" My thoughts on the STM Question...
  29. A

    Relative Motion of a moving sidewalk

    Help is much appreciated. These are extra credit problems I have. The airport terminal has a "moving sidewalk" to speed passengers through a corridor. Peter does not use the moving sidewalk; he takes 150 s to walk through the corridor. Paul, who simply stands on the moving sidewalk, covers...
  30. R

    Swimmer in river relative motion crap

    A river 570 ft wide flows with a speed of 6 ft/s with respect to the earth. A woman swims with a speed of 3 ft/s with respect to the water. a) If the woman heads directly across the river, how far downstream is she swept when she reaches the opposite bank? b) If she wants to be swept a...
  31. M

    Relative motion of an elevator question

    Okay, we're learning relative motion in class and I just want to see if I am uderstanding things correctly. Okay there is a guy in an elevator and the elevator is on the ground. Also on the ground (outside of the elvator) is a ball. A ball is shot upward with Vo = 7 m/s. At the same time, the...
  32. P

    What is the Angle of the Man's Path Relative to the Water on a Moving Ship?

    A ship cruises forward at vs = 5 m/s relative to the water. On deck, a man walks diagonally toward the bow such that his path forms an angle theta = 19 degrees with a line perpendicular to the boat's direction of motion. He walks at vm = 3 m/s relative to the boat. I found the speed at...
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