g is referred to as acceleration due to gravity. It is defined as the constant acceleration produced in a body when it freely falls under the effect of gravity alone.
The SI unit of ‘g’ is m/s^2.
It is a vector quantity and is directed towards the center of the earth.
Where G is the universal gravitational constant and its value = 6.673 x 10-11N m2 Kg-2
M = Earth’s mass = 6 x 1024 kg
r = radius of the earth = 6 kg
The value of g on earth is calculated by using the formula:
g = GM/r2
g = 6.673 x 10-11 x 6 x 1024 / (6)2
g = 9.8 ms-2
It is the net acceleration that is transmitted to bodies due to the combined effect of gravitation and the centrifugal force (from the Earth's rotation).
Its value near the earth's surface is appro x 9.8 ms-2
Ignoring the factors like air resistance and speed of object and considering the body to be freely-falling under the influence of gravity.
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The value of g remains fixed at a given place.
It varies from place to place on the surface of earth by altitude and rotation of the earth.
Table 1
Location Above Earth’s Surface | Distance from Earth’s Center (m) | g(ms-2) |
1000 km above | 7.38 x 106m | 7.33 |
2000 km above | 8.38 x 106m | 5.68 |
5000 km above | 1.14 x 107 m | 3.08 |
50000 km above | 5.64 x 107 m | 0.13 |
The same equation like we used for value of g on earth is used for calculating the value of g on the surface of other planets
Table 2
Planet | Radius (m) | Mass | g (ms-2) |
Mercury | 2.43 x 106 | 3.2 x 1023 | 3.61 |
Venus | 6.073 x 106 | 4.88 x 1024 | 8.83 |
Mars | 3.38 x 106 | 6.42 x 1023 | 3.75 |
Saturn | 5.82 x 107 | 5.68 x 1026 | 11.2 |
Neptune | 2.27 x 107 | 1.03 x 1026 | 13.3 |
Pluto | 1.15 x 106 | 1.2 x 1022 | 0.61 |
Hence, the value of g varies at different places.
The acceleration due to gravity on the surface of the moon is called the moon gravity.
The value of Moon’s gravity = 1.62 ms-2
The value of g is calculated as:
Mass of moon = 1/ 80 (1.2%) of Earth’s mass = 7.342 x 1022 kg
Moon’s radius = 1.74 x 106 m.
Using the formula
g = GM/r2
Putting the value of G = 6.673 x 10-11 Nm2 Kg-2and M and r in the above equation:
= 6.673 x 10-11x 7.342 x 1022 /(1.74 x 106 )2
On calculating we get
g(moon) =1.625 ms-2
Therefore, the value of g(moon) is 1/ 6 or 16.7% of g(earth's surface)
We can also say that the moon's gravity is 5 /6 or 83.33% less than the earth’s gravity.
Do you know why the weight of a body on the moon is 1 /6 of that on the earth?
Its because the gravitational force on the moon is 6 times lesser than the earth which is 1.625 ms-2and the weight is directly dependent on the gravitational acceleration.
Let’s discuss some facts related to the same:
You can jump close to your height on the moon.
Suppose you fire a bullet from a M-16 rifle at a perfect angle, there are high chances that bullet may fall on the other side of the moon or may even cross it.
You can easily perform activities like backflip, sidekick, 400 560 kicks and so many acrobatics without getting hurt.
You can easily perform acrobatic exercise like somersaults without belly flops, provided there’s a pool on the moon, because you’ll have a lot of time to adjust or position yourself for the perfect jump while you are on the air.
You can beat Ankita Sharma’s long jump record (8.19 meters) in a single try.
1. Write Some Facts About The Moon.
Some proven facts of the moon are:
1.The surface of the moon is usually dark.
2. The moon makes the earth and tides move.
3. The moon was made when the rock size of Mars struck earth.
2. At What Height Gravity Is Zero?
Since the value of gravity decreases with height and we would get the value of g as zero at a height of one half of the Earth’s radius
i.e., 9.8 ms^{-2} per 3200 km.
3. Can You Jump Off The Moon?
Yes, we can jump off the moon. Though we can jump very high on the moon. In order to jump off the moon, you need to travel as fast as 2 kilometer per second to escape from the moon’s surface.
4. What Is The Temperature On The Moon?
During the daytime, one side of the moon lasts about 13.5 days and has 13.5 days of darkness during half nights.
When sunlight hits its surface, the temperature can reach 260° F (127° C) and when the sun goes down, temperature reduces to - 280° F (- 173° C).
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