At what speed does a clock move if it is measured to run at a rate two-fifths the rate of a clock at rest with respect to an observer

0.44c

Explanation:

We know that

Time interval at speed (ts)= time interval at rest(tr) / gamma

where

gamma = √[1-(v/c)²]

ts = tr / gamma

tr/ts = gamma

But

Ss/Sr = gamma

Where

Sr = clock speed at rest, Ss at speed):

So

√[1-(v/c)²] = 2/5

1 - (v/c)² = 4/25

(v/c)²= 5/25

v/c = √5 / 5

v = 0.444c

hi there!

your question asks at which segment does freezing occur.

since we're talking about water, the freezing point of water will be 32 degrees fahrenheit or below.

hope this ! ~