Hello everybody! My name is Sir Isaac Newton. I discovered the law of gravity! I also discovered the three laws of motion!
This apple fell from that three.
How did this apple fall from that tree? Is the same force that pulled the apple to the ground tugging on the moon?
I have a hypothesis: All physical objects have a force of attraction between them. The strength of the force depends on the masses of the objects and the distance between them.
Let's conduct an experiment!
Let's measure the data and record the results!
I am visualizing a cannon on top of a very high mountain. If there are no forces of gravitation or air resistance, the cannonball should follow a straight line away from Earth, in the direction that it was fired. If a gravitational force acts on the cannonball, it will follow a different path depending on its initial velocity. If the speed is low, it will simply fall back on Earth.
If the speed is the orbital speed at that altitude, it will go on circling around the Earth along a fixed circular orbit. If the speed is higher than the orbital velocity, but not high enough to leave Earth altogether, it will continue revolving around Earth along an elliptical orbit. If the speed is very high, it will leave Earth in a parabolic or hyperbolic trajectory.
Let's see if your hypothesis is correct!
Congratulations Isaac! Your hypothesis is correct!