An apple with a mass of 200 grams and an orange with a mass of 120 grams are in an aquarium filled with water with a density of 1 gram/cm³. The two fruits are separated by a distance of 1 meter. How much gravitational force does the orange experience on the apple?
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00:00Hi friends, meet again with the Ribia Studio.
00:08Previously we have known the simple concept of universal gravitational force.
00:14This time, we will discuss a question related to it.
00:19An apple with a mass of 200 grams and an orange with a mass of 120 grams are in an aquarium
00:26filled with water with a density of 1 gram per cubic centimeter.
00:30The two fruits are separated by a distance of 1 meter.
00:35The question is, how much gravitational force does the orange experience on the apple?
00:45Here is a simple concept of universal gravitational force.
00:50There is an object with a mass of big M. Around it there is another object with a mass
00:58of M. The distance between the centers of mass
01:03of these two objects is R. This object will receive a gravitational force
01:10towards the other object.
01:12F is equal to big G big M M over R squared.
01:19The big G here is the universal gravitational constant.
01:23Its value is 6.67 times 10 to the power of negative 11 newton meters squared per kilogram
01:29squared.
01:31This is the formula we will use in this series.
01:39What if these two objects were separated by a medium such as water?
01:43Does this formula still apply there?
01:50That's right, it still applies.
01:52This formula does not depend on the presence or absence of a medium between the two objects.
02:01An apple on a table or an apple floating in the air will have the same gravitational force
02:06at the same height.
02:10It's just that the apple on the table also gets a normal force as large as the gravitational
02:15force, but the direction is upwards.
02:19The resultant of the two forces is zero, while the apple floating in the air has a resultant
02:26force as large as the gravitational force.
02:33Look again at our problem.
02:35We will identify the values listed on the problem sheet.
02:41The object of the source of gravity is the apple.
02:44Thus, big M is 0.2 kilograms.
02:50The object receiving the gravitational force is the orange.
02:53Thus, M is equal to 0.12 kilograms.
03:01The distance between the two objects of mass, R, is equal to 1 meter.
03:08Since the medium does not affect the gravitational force, we do not need to write the density
03:12of water.
03:15It seems that this is the only value we need.
03:19Now, we can calculate the gravitational force.
03:25F is equal to big G big M M per R squared.
03:31We can enter all the known values, especially for the value of the universal gravitational
03:38constant.
03:39You must memorize that value.
03:43F is equal to 1.6 times 10 to the power of negative 12 meters.
03:50This value is very small.
03:52The static friction force of the orange is much greater than this value.
03:56A force of this magnitude will not be able to overcome the static friction force.
04:01That is why the orange does not move towards the apple.
04:06Hopefully this tutorial is useful.
04:09And don't forget to watch the next video.