If 2 boys are running toward each other , has their velocity same frame of reference?

Question

Note what give the velocities to the boys is not the observer.

suppose the boys collide what would be the colison velocity?

Answer 1

Running, by definition, can only occur on a surface. In this case, the frame of reference is the surface on which the boys are running.

In reference to the ground both boys' velocity is relative to the ground, so YES.

Answer 2

If we assume they are running on some surface (like Earth), then there would be 3 easily used reference frames available,
1) reference frame of Boy 1
2) reference frame of Boy 2
3) reference frame of something at rest with respect to the running surface.

Using these 3 reference frames, one can obtain different measurements for each other boys' speeds.

In reference frame 1, Boy 1 is stationary, and boy 2 has some velocity v.
In reference frame 2, boy 2 is stationary and Boy 1 has some velocity -v.
In reference frame 3, both boys have some velocity which is not necessarily the same as the other boy's velocity or the velocities measure in each of the two other frames.

The collision velocity would, again, depend upon the frame of reference.

Answer 3

The question is illogical. What do you mean by their velocity? Do you mean the rate of change of the distance between them? Then you may choose various reference frames and the velocity will not depend upon the choice of reference frame.

For instance, if the frame is centered at boy A, and the rate of closure is V, then if you switch to a frame centered on boy B, the velocity remains V. You may choose any arbitrary linearly moving reference frame under local relativistic assumptions and this will be true.

If you mean that each boys velocity, measured separately, has the same frame of reference, then no, you can choose separate frames for either boy. And what does towards each other constitute? If boy A is in the Philippines and headed north, and boy B is in Ecuador headed north, they are running towards each other in one frame, and parallel to each other in another, both with the same velocity.

Hope that helps.

Answer 4

The statement that two boys are running toward each other is stated by you. It is not the statement of either of the two boys. Therefore, with respect to you the two boys are running.

Thus the reference frame is the frame where you are and the two velocities are in this (your) reference frame and they are oppositely directed with respect to you. Therefore their velocities have the same frame of reference.

Suppose the two boys are A and B and you are designated by O. You can shift your origin of reference frame at your will to any point. For example you can shift the origin to the point where A was at an instant of time or to the point where B was at an instant of time or any other point convenient to you. Your statement about the two boys will be the same irrespective of the position of origin and their velocities will have the same reference frame.

The statements and velocities will be different by A or B, if they choose a reference frame which is moving along with them. For example, A will say that B is moving with a velocity in a particular direction. He will not say that they are moving toward each other unless he choose a reference frame in which that statement will be valid.

Answer 5

If you consider the earth a frame of reference, then yes, their velocities can be compared to that frame.

If you just say that they are running, that does not give any reference frame.

Answer 6

no, you have to pick a frame. Either boy 1, boy 2, or some 3rd frame.

Answer 7

if they have the same velocity, and assuming that all forces net =0, and that there are no fixed points to look at, they still appear to be running. now if they were just randomly walking forward without visibly moving, then yeah, he would look like he's moving and you're standing still, and vice verse.