a) <em>Fixed points</em> are the temperatures at which a thermometer is calibrated. They can refer either to the actual temperatures used for calibration, or the thermometer readings at those temperatures.
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b) <em>Fundamental interval</em> is the difference between the fixed points. As with fixed points, it can refer either to the difference in actual temperature, or the difference in the corresponding thermometer readings.
means that a body is in motion, and its velocity is measured in meters per second. And, that velocity is increasing by two meters per second, every second.
rad/s
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rad/s