I am 11 year old and I don't known the answer to this question
A voltmeter<span> its </span>instrument<span> used for </span>measuring<span> electrical potential difference between two points in an electric circuit. </span>An ammeter<span> is a </span>measuring device<span> used to</span>measure<span> the electric current in a circuit.
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Vs - velocity on beginning
ve - velocity on ending. You've got:

So he needed 4 second.