Relative Velocity of a Car on a Moving Truck

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In summary, the conversation involves a physics question about the speed of a car relative to the ground when it is traveling on a flat bed truck with an infinitely long bed. The answer is 65 miles per hour and the explanation involves Galilean Relativity and the "addition of velocities" formula. It is also noted that for higher speeds, Einstein's special relativity and a different formula is needed.
  • #1
JackRuby
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I was just asked a physics type question that is puzzling me. Perhaps I'm over thinking it.

Q. Suppose that there is a flat bed truck traveling at 30 miles/hour relative to the ground. The truck has an infinitely long bed. A car (sitting) on the bed is traveling at 35 miles and hour relative to the truck bed (per its speedometer). What is the speed of the car irelative to the ground? Assume that the car is traveling the same direction.

My guess is 65 Mi/hr

What is the technical explanation?
 
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  • #2
Galilean Relativity

You are correct. It's an example of the "addition of velocities" formula:
[tex]V_{a/c} = V_{a/b} + V_{b/c}[/tex].

This also illustrates what is called Galilean relativity, or how to transform from one moving frame to another.

Note that if the speeds involved are high enough, one must use Einstein's special relativity and a different formula for velocity addition to get an accurate answer.
 
  • #3
Great!

Thanks...

I appreciate your help.

JR
 

FAQ: Relative Velocity of a Car on a Moving Truck

What is the theory of relativity?

The theory of relativity is a scientific theory developed by Albert Einstein that explains how gravity works and how objects move through space and time. It consists of two parts: the special theory of relativity and the general theory of relativity.

How does the theory of relativity differ from Newton's laws of motion?

The theory of relativity differs from Newton's laws of motion in that it takes into account the effects of gravity and the curvature of space-time. Newton's laws only apply to objects moving at constant speeds in a flat space-time.

What is the difference between special relativity and general relativity?

Special relativity deals with the laws of physics in inertial frames of reference, while general relativity includes the effects of gravity and non-inertial frames of reference. General relativity is a more comprehensive theory that can explain the behavior of objects in all types of frames of reference.

What are some practical applications of the theory of relativity?

The theory of relativity has many practical applications, such as GPS systems, which use relativity to account for the time dilation effect of satellites orbiting the Earth. It also helps in understanding the behavior of objects in extreme environments, such as black holes.

Is the theory of relativity proven?

The theory of relativity has been extensively tested and confirmed through numerous experiments and observations. It is considered one of the most well-established and successful theories in physics.

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