how is gravity measured
In: 8
By seeing how much force is exerted on a known mass. Mass is a measure of how many electrons, protons and neutrons are in a particular thing. This number doens’t change, it doesn’t matter if you’re on top of Mt Everest or on Mercury. Gravity is a measure of how much force is exerted on that mass.
Earth gravity acceleration: using pendulum (measure its period) or rolling a ball on a ramp (measure its time)
Gravity constant in general between two masses: [Cavendish experiment](https://www.youtube.com/watch?v=11sLusnVZwM)
You take something, and you drop it. You measure how fast it accelerates. It’s that simple.
All masses accelerate due to gravity at the same rate (if you ignore air resistance).
F=mg
F=GMm/r^2
mg=GMm/r^2
g=GM/r^2
gravitational acceleration = constant * mass of Earth / radius of Earth^2
It doesn’t depend on the mass of what you drop.
With the initial setup running the same experiment all over Earth, we can even see how gravity varies all over the planet. Canada and the Indian Ocean have lower gravity than most of the rest of the world.
Gravity is a force, so you can measure it in newtons (metric) or pounds (imperial). Newton’s equation, which is technically only an approximation but works fine for most common applications, is:
F = G(m1)(m2)/r^2
Where F is the force of gravity, m1 and m2 are the masses of the two objects involved (e.g. the Earth and you) and r is the distance between the objects, and G is something called the gravitational constant.
When talking about gravity on the surface of a planet like Earth, you can basically consider one of the masses (the planet) and the radius r (the size of the planet) constant, meaning that the force of gravity is directly proportional to the mass of the second object.
You might remember another of Newton’s laws which says that force equals mass times acceleration, so gravity is often described in terms of acceleration units, e.g. Earth’s gravity is commonly quoted as 9.8 m/s/s (though technically it depends on your altitude and where exactly you are).
Latest Answers