Classically we would add the speeds to get $1.8c$, which is obviously not allowed. In relativity you simply use the relativistic velocity addition formula:

Sep 19, 2018 · An object of mass $2 \,{\rm kg}$, moving with speed of $12\,{\rm m/s}$, collides head-on with a stationary object whose mass is $6 \,{\rm kg}$. Given that the collision is elastic, what are the final velocities of the two objects? Neglect friction. Using the velocities of approach and separation one might proceed as follows.

May 15, 2018 · A passenger in a vagoon walking against the train direction, etc. There are some examples on this If a passenger in a vagoon walking against the train direction, of course the train speed is greater and v_n = v_t - v_p is the speed. In this formula v_n is the net speed and v_t and v_p are train speed and passenger walking speed respectively. If there is a river flowing at a …

Jan 4, 2019 · If you shoot one object to the east with speed 0.75 c and one object to the west with speed 0.75 c, then in your frame of reference the relative speed of the objects will be 1.50 c. But in the frames of each of these objects, the other object will have a speed of only $0.96 c.$

May 27, 2014 · What is the speed of light relative to? It is relative to you and all other objects, in direction and measure. As mentioned by physicist Brian Greene in his book The Elegant Universe, see The_Elegant_Universe-B.Greene.pdf Motion Through Space-Time pages 26 and 27, all objects are constantly on the move within Space-Time at the speed of light.

If I start applying a force greater than the kinetic friction force, the box will speed up. Will it keep speeding up indefinitely, or will the kinetic friction force I need to overcome increase as the box gets faster?

Jul 7, 2015 · All these spacetime bending consequences used to explain why nothing can move past this speed only seems to enshrine the concept that there is some ultimate speed standard. If there is only relative speed, then the concept of light having a specific speed in the vacuum should be a nonsensical one since it having speed (x m/s) would only make ...

Relative to this frame, the local group of galaxies is moving at about 600 km/s (Wikipedia gives precise numbers and probably citations that I'm too lazy to look up). People sometimes worry about whether the existence of a preferred "rest frame" of …

Yes, it is 2c and this does not violate the principles of relativity, because such speed is not the speed of a particle, but it is just a derived value. On the other hand, the speed of a photon is c regardless of the inertial frame, and is calculated by the relative speed formula, given in the previous answers.

Oct 10, 2014 · As you propose let's find a "trick" and take advantage of the relative speed of the vehicles. Let's find out when they meet first. Let's imagine we are sitting in the slower vehicle. We say we are "in a frame of reference attached to the slower vehicle". From our perspective the faster vehicle is moving towards us at 50-25 = 25km/h.