A spaceprobe has an 29.0 m length when measured at rest. What length

does an observer measure when the probe is going by at a speed of 0.95c?

The observer sees the space-probe 9.055m long.

Explanation:

Let be the length of the space-probe when measured at rest, and be its length as observed by an observer moving at velocity , then

Now, we know that and , and putting these into we get:

Thus, an observer moving at 0.95c observes the space-probe to be 9.055m long.

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