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- Thread starter DrWafflez Jr.
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DennisN

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No. At relativistic speeds, you can not add velocities like you usually do, because of special relativity. See Velocity-addition formula (Wiki) and Einstein Velocity Addition (HyperPhysics).So the obvious question, if that is true can we go the speed of light?

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Ryan_m_b

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Honk the horn and the sound will travel at the speed of sound no matter the speed of the source - sound waves have a particular speed in the air and that's the speed the move at.I have a question, my bestfriends dad said that if we were driving at 70 mph and then honked the horn, the sound would go 70 mph + the speed of sound. .... Last but not least can this be accomplished with a gun being shot or something of the sort? Thanks in advance

Fire a bullet forward from a moving car and the speed of the bullet relative to the ground will be given by the velocity addition formula DennisN mentions (##\frac{u+v}{1+uv/c^2}##) where ##u## is the speed of the car relative to the ground and ##v## is the muzzle velocity of the bullet. For cars and bullets and other slow-moving objects (here "slow-moving" means not tens of thousands of miles a second) this formula reduces to the ##u+v## that common sense tells us to expect.

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