The SI unit of pressure is
- A.Newton
- B.Pascal
- C.Hertz
- D.Tesla
Correct answer
Explanation
The correct answer is B, pascal. Pressure is force divided by area, so its unit is one newton per square metre, which is given the name pascal after Blaise Pascal. Its dimensional formula is M L⁻¹ T⁻², and atmospheric pressure at sea level is about 1.013 lakh pascals, also written as one atmosphere or about 1,013 millibars.
Option A, the newton, measures force itself and not force per unit area; this is the commonest confusion in the question. Option C, the hertz, measures frequency, that is the number of cycles per second. Option D, the tesla, measures magnetic flux density. Remember that the instrument used to measure atmospheric pressure is the barometer, and a sudden fall in its reading warns of a storm. Two other units of pressure are worth knowing: the bar, which is one lakh pascals, and the torr, the pressure of one millimetre of mercury.
Read the full article: Units and Measurements: SI Units, Dimensions and Instruments
Practice Questions
View allWhat is the SI unit of force?
- A.Joule
- B.Newton
- C.Watt
- D.Pascal
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One newton is the force that gives a mass of one kilogram an acceleration of one metre per second squared, which follows directly from the equation force equals mass times acceleration.
Read the full explanation →How many base units are there in the International System of Units (SI)?
- A.Five
- B.Six
- C.Seven
- D.Nine
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The SI system, adopted in 1960 by the General Conference on Weights and Measures, rests on seven base units: the metre, the kilogram, the second, the ampere, the kelvin, the mole and the candela.
Read the full explanation →Which one of the following is NOT a base unit of the SI system?
- A.Kelvin
- B.Mole
- C.Newton
- D.Candela
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The newton is a derived unit: it is built from the kilogram, the metre and the second, since force equals mass times acceleration, and it can be written as one kilogram metre per second squared.
Read the full explanation →The candela is the SI unit of which physical quantity?
- A.Luminous intensity
- B.Electric current
- C.Amount of substance
- D.Pressure
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The candela takes its name from the candle, which was once used as a rough standard of light, and it is one of the seven base units of the SI system.
Read the full explanation →A light year is a unit of which of the following?
- A.Time
- B.Distance
- C.Speed
- D.Brightness of a star
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A light year is the distance that light, moving at about three lakh kilometres per second, covers in one year, which works out to roughly 9.46 trillion kilometres.
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