what is meant by relative velocity?

Answer 1

Example: If you are going at, say, 15 mph on a road and you are passing another car going 10mph, your relative velocity in relation to that car is +5mph.

Answer 2

The velocity of a body with respect to another body is called relative velocity. For example a person travelling in a train has no velocity with respect to train. But for a person observing him on the ground it seems to have velocity to the person travelling in the train. This is called relative velocity.

Answer 3

We measure the height at which a bulb hangs from the floor of the room. Say it is 3m.

But the room is situated on the top most of the multistoried building.

The floor of the room is 50 m above the ground.

From the ground the bulb is at 53m.

Thus the height differs upon the origin of the measurement.

It is relative to the origin of the measurement.

Similarly speed or velocity is also relative.

We measure the speed of a ball that rolls on the floor as 5m/ s.

But the floor is the floor of a moving train which is moving in the direction of the motion of the ball with a speed of 30m/s.

For a person in the station, the train is moving with a speed of 30 m/s and the ball is moving with a speed of 30 + 5 = 35m/s.

But for us who are inside the train (or with respect to us), the ball is moving with a speed of 5 m/s and the train is at rest.

Thus the velocity is different for different observers. It is relative to the observer. It is relative velocity.

Answer 4

All velocity is relative velocity...in fact, that's one of the fundamental tenets of the relativity theories, which is why they are called the theories of relativity.

Velocity is simply a change in position relative to some framework over some period. We often designate it like v = del(S)/del(t); where v = velocity, del means "change in", S is a measure of distance relative to some coordinate system, and t = time. Let's look at some relative velocities.

Suppose you get up from your table and walk 88 feet to a nearby bar in 2 seconds to order a drink. What is your velocity with respect (relative) to the floor of the bar? Clearly, that's v = del(S)/del(t) = 88/2 = 44 ft/sec. So you walk very briskly (because you are really thirsty) at 30 mph (44 ft/sec) to the bar.

Simple enough...but what if I told you the bar was really on a railroad dining car of a train going 60 mph? How fast are you walking relative to the ground rather than to the floor of the bar?

In two seconds that train covers 176 feet; so, assuming the train and you are going the same direction, you have to add that distance to the distance walked through the dining car, which was 88 feet if you recall. Thus, relative to the ground, you walk (travel) 264 feet in two seconds rather than the 88 feet relative to the dining car. Thus, with respect to the ground, you travel v = del(S)/del(t) = 264 ft/2 sec = 132 ft/sec, which is 90 mph. Which is a good result because, intuitively, we would just add the speed of the train (60 mph) to the speed of walking (30 mph) through the car to find the velocity relative to the ground (90 mph).

Even while you are standing still, relative to the Earth, your relative speed with respect to the Sun is over a thousand miles per hour. From rotation alone, you are traveling over 1,000 mph due to the spin of the Earth. Then you have to add the velocity of the Earth as it speeds around in orbit to that 1,000 mph; so you see, your relative velocity, with respect to Earth is zero, but relative to the Sun it's thousands of miles per hour.

Thus, as asserted at the outset, all velocity is relative to something. They are all relative velocity.

Answer 5

For velocity to mean anything you need a reference.... Let's say you're standing still and someone jogs by you at 5 mph...to you it looks like the other person is going 5 mph. But maybe you both are inside of a car on a train going 60 mph....To you the jogger still looks like he's going 5 miles per hour, to a person standing on the ground outside looking in through a window it might look like the jogger is going 65 mph (speed of train + speed of jogging)....and to someone standing on a different train going the opposite direction it might look like he's going 125 mph (speed of both trains + speed of jogging). So how fast is the jogger going? 5 , 65, 125 mph? Without knowing a reference point you can't give a good answer, you can only tell how fast he's going relative to some other object.

Answer 6

It is not only velocity but everything is relative in this universe. Without a relationship or the ability to relate, a human will be lost and can not survive.

Answer 7

The speed of one object relative to another. For example, a car is travelling at 100km/h east, and another car is travelling 50km/h west. The speed of each is 100km/h and 50km/h relative to the ground, but the speed of one car relative to the other is 150km/h.

You need to treat this as vectors, not just simple addition. So, draw a line 100mm long in one direction, and 50mm long in the other. The distance from one endpoint to the other endpoint is the relative speed. If the two cars are travelling in the same direction, then draw a 100mm line and 50mm line in the same direction (on top of each other, in this case). The distance between the endpoints would be 50mm, so the relative speed would be 50km/h.

It gets a bit more complicated when one car is going north and another east, but there are forumlas for that, too (pythagorean theorem, or sin/cos if the angle isn't 90 degrees).

Answer 8

It's my velocity measured from your reference frame. If you see me standing on a platform of a station from inside a train going 70 mph, my relative velocity to you is 70. But from my standpoint, you are going 70 relative to me. Let not get into what happens when your train is going close to the speed of light!

Answer 9

Relative velocity is a measurement of velocity between two objects moving in different frames of reference.

Answer 10

When two objects collide, their coefficient of restitution gives a measure of the elasticity of the collision. An elastic collision is one in which kinetic energy is conserved. In practice some k.e. is always converted into other forms. Which other forms?
If we compare the relative velocity of the two objects just before the collision (velocity of approach, va) with their relative velocity just after the collision (velocity of separation, vs) we can see "how elastic" the collision was.
Coefficient of restitution = e

e = vs/va

e = 1 for totally elastic collision
e = 0 for totally inelastic collision

Answer 11

The relative velocity of an object in motion with respect to another is the vector difference between their velocities.
Suppose u r traveeling north with a velocity 20 km/h & I m travelling south with a vel. 30 km/h
then the relative vel of u wrt me = 50 km/h north.