physics ch9 cont.

Calculate the force of gravity on the same 1kg mass if it were 6.4 x 10⁶m above earth's surface (that is, if it were two earth radii from earths center.)

F = G m₁1m₂/d ² 6.67x 10 −¹¹ N x m² /kg² x (1kg )(6 x 10²⁴ kg )/ [2(6.4 x 10⁶m)]² = 2.5N

Calculate the force of earth's gravity on a 1kg mass at earths surface. the mass of earth is 6.0 x 10²⁴kg and its radius is 6.4 x 10⁶m. Does the result surprise you?

F = G m₁1m₂/d ² 6.67x 10 −¹¹ N x m² /kg² x (1kg )(6 x 10²⁴ kg )/ (6.4 x 10⁶m)² = 9.8 N .

Calculate the force of gravity a newborn baby of mass 3.0kg and the obstetrician of mass 100.0kg exerts on each other when the distance between them is 0.5m. Which exerts more gravitational force on the baby: Mars or obstetrician? By how much?

F = G m₁1m₂2/d ² 6.67x 10 −¹¹ N x m² /kg² x (3.0kg )(100kg )/ (0.5m)² = 8.0 x 10−⁸N The obstetrician exerts about twice as much gravitational force

Calculate the force of gravity a newborn baby (mass 3.0kg) and the planet mars (mass 6.4 x 10²³kg) exerts on each other when mars is at its closest to earth (distance 5.6 x 10¹⁰m).

F = G m₁1m₂2/d ² 6.67x 10 −¹¹ N x m² /kg² x (3.0kg )(6 x 10²³ kg )/ (5.6 x 10¹⁰m)² = 4.1 x 10−⁸N

Calculate the force of gravity that earth and the sun exert on each other (sun's mass is 2.0 x 10³⁰kg average earth-sun distance is 1.5 x 10¹¹m).

F = G m₁1m₂2/d ² 6.67x 10 −¹¹ N x m² /kg² x (6 x 10²⁴ kg )(2.0 x 10³⁰kg)/ (1.5 x 10¹¹m)² = 3.6 x 10²²N

Calculate the force of gravity that earth (mass 6.0 x 10²⁴kg) and the moon (mass 7.4 x 10²²kg) exert on each other. The average earth-moon distance is 3.8 x 10⁸m.

F = G m₁1m₂2/d ² 6.67x 10 −¹¹ N x m² /kg² x (6 x 10²⁴ kg)(7.4 x 10²² kg)/ (3.8 x 10⁶m)² = 2.1 x 10²⁰ N