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Class 11
Physics
Unit & measurment
a calorie is a unit of heat or energy and it equal...

Question:
A calorie is a unit of heat or energy and it equals about 4.2 J where 1J = 1 kg m²s^–2. Suppose we employ a system of units in which the unit of mass equals α kg, the unit of length equals β m, the unit of time is γ s. Show that a calorie has a magnitude 4.2 α^–1 β^{– 2} γ² in terms of the new units.

Answer:

Given that, 1 Calorie=4.2 J = 4.2 Kg m² s^-2 ...... (i)

As new unit of mass = α Kg

∴ 1 Kg = 1/α new unit of mass

Similarly,

1 m = β^{– 1} new unit of length

1 s = γ^-1 new unit of time

Putting these values in (i), we get

1 calorie = 4.β (α^-1 new unit of mass) (β^{– 1} new unit of length)β ( γ^-1 new unit of time)^-2

= 4.β α^-1 β^{– 2} γ² new unit of energy (Proved)

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