30_field_strength - Lesson 30 Gravitational Field Strength...

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Lesson 30: Gravitational Field Strength In the last lesson we were able to combine our two formulas for force due to gravity to get a new formula. F g = F g m test g = Gm test M e r 2 g = GM e r 2 The great news is that the mass (shown above as the mass of the Earth “M e ”) can actually be any mass. It could be the mass of the moon, Mars, an asteroid, whatever! In fact, we should replace mass of the Earth in the formula with just mass , since it can be any mass. g = Gm r 2 g = gravitational field strength (m/s 2 ) G = Universal Gravitational Constant m = mass of object producing the field (kg) r = distance from centre of mass (m) This formula lets you calculate the the gravitational field strength (the acceleration due to gravity) caused by that mass ata specific distance from its centre. Example 1 : The planet Mars has a mass of 6.42e23 kg and a radius (from its centre to the surface) of 3.38e6 m. a) Determine how much a 60.0 kg person would weigh on Mars. b) Compare it to his weight on Earth. c) Determine how heavy the 60.0 kg person would “feel” as an apparent mass in kilograms on Mars. a) To determine someone's weight, we first need to know the acceleration due to gravity on Mars. g = Gm r 2 g = 6.67e-11 6.42e23 3.38e6 2 g = 3.75 m / s 2 So the person's weight will be. .. F g = mg F g = 60.0 3.75 F g = 225 N 7/6/2007 © studyphysics.ca Page 1 of 4 / Section 4.3
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b) On Earth the person has a weight of… F g = mg F g = 60.0 9.81 F g = 589 N Probably the easiest way to compare the person's weight on Mars and the Earth is to find the ratio of the two. F
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This note was uploaded on 12/02/2011 for the course PHYSICS 235 taught by Professor Staff during the Fall '08 term at Rutgers.

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30_field_strength - Lesson 30 Gravitational Field Strength...

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