Relative velocity Definition and 416 Threads

A swimmer is training in a river. The current flows at 1.99 metres per second and the swimmer swims upstream a distance of 153 metres before swimming back to the starting point. If the total time for the swim is 192.0 seconds, what is the swimmer's speed relative to the water? I've been stuck...

Is it meaningful to talk of relative velocity between two moving points at a distance in curved space-time? This interesting issue came up in the course of discussion of the thread "Curved Space-time and the Speed of Light".I remember Dalespam giving some formidable logic with a very good...

Homework Statement An airplane is heading due south at a speed of 600km/h. If the wind begins to blow from the southwest at a speed of 100km/h (average), calculate: a) The velocity (magnitude and direction) of the plane relative to the ground b) How far from its intended position will it be...

Consider the usual example of relativity - train and the observer on the platform. Now, the observer is moving according to the train and the train is moving according to the observer. But we know that it is the train which is spending the energy to move forward. We can neglect the friction...

I want to calculate the instantaneous relative velocity between two objects. Object A is at location (x1,y2) moving towards the origin (0,0) at velocity V. How do you calculate object A's relative velocity to object B at location (x2,y2)?

Homework Statement A wind is blowing at 25 km/h from the direction of 270 degrees . Find the magnitude and direction of the velocity of the wind relative to a cyclist traveling at 20 km/h in the direction of 120 degrees . Homework Equations The Attempt at a Solution Using the...

Homework Statement A car A and a bicycle B are moving along two straight roads which cross at O at 90 degree . A moves to the east at a constant speed of 48km/h , whereas B moves towards the north at a speed of 14 km/h . At the time when B passes O , A is 400 m away from O and has yet to...

Homework Statement A particle , P moves on a horizontal plane along the circumference of a circle with centre O and a radius of 3m at an angular velocity of pi/4 rad/s in the clockwise direction . A second particle , Q moves on the same plane along a circle with radius 2m and the same centre...

on a two lane road, car A is traveling with a speed of 36km/h. two cars B and C approach car A in opposite direction with a speed of 54km/h each. at a certain instant, when distance AB is equal to AC both being 1km, B decides to overtake A before C does. what minimum acceleration of B is...

Dont know if this has been discussed here before.. If two relativistic particles are traveling with speeds 'u' &'v' ,how to calculate the relative velocity?

Homework Statement Spaceship A and spaceship B are each a proper length 100.0 m and travel at constant velocities. The spaceships pass in outer space while traveling in opposite directions. The pilot of A observes that 2 microseconds elapse while spaceship B passes by the cockpit window...

Homework Statement Man can swim 3m/s in the water, water flows 5m/s. River is 176 m wide Find direction at which a) he will end up as little downstream as possible, b) as quick as possible. 2. The attempt at a solution For b) I think it would be the fastest speed possible i.e. 90...

Homework Statement A swimmer can swim at a speed of 1.80m/s in still water. If the current in a river 200m wide is 1.0m/s [E], and the swimmer starts on the south bank and swims so that she is always headed directly across the river, determine: a) The swimmer's resultant velocity, relative to...

Im taking physics now and I am trying to study for an exam but some of the sample questions in my textbook do not give a an explanation of how to solve them...it's ridiculous. Do they think it will just come to me?! Question:Suppose the river is moving east at 5.00km/h and the boat is...

Homework Statement a plane flies at an airspeed of 250 km/h. A wind is blowing at 80 km/h toward the direction 60(degrees) east of north. a) in what direction should it fly in order to fly north relative to the ground? b) what is the speed of the plane relative to the ground?Homework...

Homework Statement Two piers, A and B are located on a river: B is 1500 m downstream from A. Two friends must make round trips from pier A to B and back. One rows a boat at a constant speed of 4 km/hr relative to the water; the other walks on the shore at a constant speed of 4 km/hr. The...

Homework Statement Two piers, A and B are located on a river: B is 1500 m downstream from A. Two friends must make round trips from pier A to B and back. One rows a boat at a constant speed of 4 km/hr relative to the water; the other walks on the shore at a constant speed of 4 km/hr. The...

Homework Statement A jet flies with an airspeed of 310 mph due east (assuming +x is due east). It is climbing vertically with a velocity of 50 mph. A wind blowing toward northeast has a speed of 55 mph. Homework Equations Find the x,y,z components of the plane's velocity relative to...

Using this diagram as an example http://img25.imageshack.us/img25/231/diagramig.jpg would I be right in assuming that the relative velocity of the boat with respect to the velocity of the current is the speed at which its moving away from say a stone floating down the river? In other words the...

Homework Statement Relative velocity question. A power boat has cruising speed of 60 km/hr. It is taking part in a race around three buoys arranged in an equilateral triangle. The second buoy, B, is 5 km due East of the starting/finishing buoy, A. The third buoy, C, is to the North of the...

Homework Statement A plane flies flies into a 65 mi/h headwind. On the return trip from B to A, the wind velocity is unchanged. The trip from B to A takes 65 min less than the trip from A to B. What is the airspeed (assumed constant) of the plane? a. 480 mi/h c. 530 mi/h b. 610 mi/h d...

Homework Statement So you've got two people standing on a boat, everything at rest, and the masses of both people as well as the boat are known. Let's call them Richard and Sandra, so the variables are Mr (mass of Richard), Ms (mass of Sandra), and Mb (mass of boat). When one of these...

Homework Statement A 56-kg woman contestant on a reality television show is at rest at the south end of a horizontal 141-kg raft that is floating in crocodile-infested waters. She and the raft are initially at rest. She needs to jump from the raft to a platform that is several meters off the...

If you are running towards a mirror at 5m/sec, at what speed is your reflection moving towards you?

Homework Statement An airplane has a speed of 280 km/h with respect to the air. There is a wind blowing at 100 km/h at 30° north of east with respect to Earth. In which direction should the plane head in order to land at an airport due north of its present location? Homework Equations...

An airplane is heading due west. The airplane's speed relative to the air is 150.0 km/h. If there is a wind of 24.4km/h toward the north, what is a) the magnitude (km/h) I used the equation sqrt 150.0^2+24.4^2 =151.97 b)what is the direction (degrees measured from west) of the velocity...

Homework Statement While driving north at 25 m/s during a rainstorm you notice that the rain makes an angle of 38 degrees 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. From these...

Homework Statement A car of length 4m and a bus of length 12m are traveling in the same direction 20m apart. The cars current velocity is 10m/s and the buses current velocity is 20m/s, the car suddenly starts to accelerate at 5m/s^2 and stops accelerating after 5 seconds. How long does it take...

Homework Statement GIVEN a plane has to complete 300 Km NorthEast in 45 min.The wind is blowing from the North at 80 Km/h .Determine the direction of heading of the plane and the velocity reqiured to complete the distance in the specified time. Homework Equations The Attempt at a...

1. The problem statement, all variables and given/known dat So a child is running with the conveyer belt. Relative to the conveyer belt he is running 2.5 m/s. Homework Equations To find the relative velocity of the child to earth, I'm guesing is: Velocity of child relative to earth= (v of...

1. A swimmer heads directly across a river, swimming at 1.7 m/s relative to the water. She arrives at a point 44 m downstream from the point directly across the river, which is 76 m wide. (a) What is the speed of the river current? 1 m/s (b) What is the swimmer's speed relative to the...

Homework Statement Here is the problem. Homework Equations Va/b = Va - Vb The Attempt at a Solution s - swimmer w - water Vw = 0.3m/s Vs/w = 2.5m/s therefore, Vs - Vw = 2.5m/s Vs - 0.3m/s = 2.5m/s Vs = 2.8m/s Now I am a bit confused at this point. It is...

Homework Statement A proton and an antiproton are moving toward each other in a head-on collision. If each has a speed of 0.8c with respect to the collision point, how fast are they moving with respect to each other? Homework Equations Ux = [U'x + V] / [1 + (v/c^2) Ux'] The...

Homework Statement Two boat landings are 5.1 km apart on the same bank of a streamthat flows at 3.4 km/hr. A motorboat makes the round trip between the two landings in 1.5 hr. What is the speed of the boat relative to the water? Answer in units of km/hr. Homework Equations The...

Hello I'll make it quick Boat is traveling at 10m/s the sea is traveling at 5m/s. What is the speed of the boat relative to the sea and why? Through vectors I worked it out to be 10m/s(not sure) but shouldn't it be five because if a person is standing in the sea and sees the boat it would be...

1. Homework Statement A helicopter 8.50 m above the ground and descending at 3.50 m/s drops a package from rest (relative to the helicopter). Just as it hits the ground, find a) the velocity of the package relative to the helicopter and b) the velocity of the helicopter relative to the...

1. The problem statements, all variables and given/known data 1. A plane leaves the ground and rises at an angle of 25º. If its speed relative to the ground is 210 mph, what is its speed relative to the air? A. 232 mph B. 210 mph C. 190 mph D. 89 mph 2. What happens to water molecules when...

hi guys I am new to this forum so this is my first post would appriciete some help with this problem Homework Statement in a colliding beam experiment, in a laboratory frame equal and opposite velocity proton beams collide. the relative velocity of the beams is 2.99 x 10^8 m/s, calculate...

Ok I am confused. As far as I understand it, in SRT two observers will agree on their relative velocity. How do they calculate it? v = \frac{\mathrm{d}x}{\mathrm{d}t} In my rest frame. But in the others rest frame:v' = \frac{\mathrm{d}x'}{\mathrm{d}t'} but now for me the length is contracted...

Homework Statement Some friends and I were working on some physics questions and when it came to this one, we all got different answers. An 90 kg logger is standing on a 400 kg log floating at rest in a pond. The logger starts to walk along the log at 1.5 m/s relative to the water. How...

1.1. A motorboat going downstream overcame a raft at point A; T=60 minutes later it turned back and after some time passed the raft at a distance l=6.0 km from the point A. Find the flow velocity assuming the duty of the engine to be constant...

Homework Statement A space vehicle is traveling at 5300 km/h relative to the Earth when the exhausted rocket motor is disengaged and sent backward with a speed of 97 km/h relative to the command module. The mass of the motor is four times the mass of the module. What is the speed of the...

I'm studying for an exam and this is one of the sample questions which I cannot figure out. Homework Statement Two ships A and B move with constants speeds 48 km/h and 60 km/h respectively. At a certain instant ship B is 30 km west of A and is traveling due south. Find: i) The...

Homework Statement Heather in her Corvette accelerates at the rate of <3.20, -2.00>m/s^2, while Jill in her Jaguar accelerates at <1.00, 3.20>m/s^2. They both start from rest at the origin of an xy coordinate system. After 5.50 s, (a) what is Heather's speed with respect to Jill, (b) how...

Homework Statement Cars A and B are going around a left-hand turn. car B is turning with radius 96m. Car A is to the right of car B and is turning with radius 100m. Car A is passing car B with relative velocity of 1 m/s. Knowing that the speeds of both cars are constant and that the relative...

Homework Statement The escalator that leads down into a subway station has a length of 30.0 m and a speed of 1.8 m/s relative to the ground. A student is coming out of the station by running in the wrong direction on this escalator. The local record time for this trick is 11 s. Relative...

Homework Statement Two trains A and B, 125m and 100m long respectively are moving in opposite directions on parallel tracks. the velocity of the train B is three times that of train A. The train takes 4s to pass each other, calculate the velocity of each train? Homework Equations Velocity=\frac...

Homework Statement In an anniversary celebration of Marilyn Bell's 1954 crossing of Lake Ontario a swimmer set out from the shores of New York and maintained a velocity of 4m/s [N]. As the swimmer approached the Ontario shore, she encountered a cross current of 2m/s [E 25deg S]. Find her...

Homework Statement Two particles of masses m and 3m are moving toward each other along the x-axis with the same speed v. They undergo a head-on elastic collision and rebound along the x- axis. I don't seem to be getting the right answer...I would really appreciate it if someone could...

Homework Statement There is an inclined plane(mass M) with inclination theta kept on a frictionless surface. A block of mass m is kept on it which is allowed to slide due to gravity. Find the accleration of the block with respect to to incline. The Attempt at a Solution The problem with this...