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| Inertial Mass and Gravitational Mass |
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| The mass of a body can be determined by measuring the acceleration 'a' produced in it by a known force 'F'. |
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| Thus, the inertial mass can be determined. |
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| The mass of a body can also be determined by the gravitational force exerted on it by the Earth. |
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| Thus, gravitational mass can be determined. |
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| Equivalence of gravitational and inertial masses |
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| We know F = mia |
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| Let us consider another body of inertial
mass mi' and acceleration a'. Let its gravitational mass be mg|. |
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| From (1) and (2), |
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| For freely falling bodies, the acceleration due to gravity is the same, irrespective of the mass. |
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Newton performed experiments with a simple pendulum. He
measured the time period  of a hollow bob filled with different substances. He concluded from his observations that mi = mg. |
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| Hence, inertial and gravitational masses are equivalent. |
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