Gravity accelerates an object by changing the direction of movement of an object without changing the speed of the object.
The apparent acceleration of an object falling to the ground is really a change in direction of a moving object. The following explanation will clarify this statement.
For clarity, we define speed, velocity and acceleration as used in this text.Speed of an object is the measurement of the distance covered in a certain time. That distance can be a strait line, a curve line or any form.Velocity of an object is the measurement of the distance covered in a certain time in one direction in a strait line.Acceleration of an object is the measurement of the change of velocity per second. It could be a change in velocity or a change in direction or a change of direction and velocity.In a clock with a needle for seconds, the tip of the needle makes one trip around in one minute, at constant speed. Its direction changes all the time but the speed remains constant. Because the direction changes, we say it has an acceleration.
We consider here a 1 kg mass located 10 meters from the surface of the earth. The explanations is similar for all objects in universe.
Before releasing the 1 kg, the object seems at rest compare to the floor of the laboratory. In reality, because the planet makes a full rotation every 24 hours, the object is moving east. Depending on the distance from the equator, the speed is different. In Ottawa, Ontario, the speed is close to 340 m/s directed parallel to the ground. It also have a speed directed downward at about an average of 5 m/s.
If the object after one second has traveled 340 m in space and is still above the ground, it is because it has two directions in its speed. A horizontal direction that has a value of 340 m / s and the other vertical which has a value of about 5m / s. In physics this is demonstrated by arrows called vectors.
The arrow that is angled downwards is called the resulting speed when the two speeds are added together. The large horizontal arrow to the east represents the speed of 340 m / s and the down arrow represents the speed of 5 m / s. This drawing is not to scale because we would not see the small arrow down.
In addition, the whole solar system is moving at 220 kilometres per second. Since we are looking at what happens in the lab, we do not have account that in our explanation.
Because the force of gravity is coming from all directions of space, the net force going horizontally is close to zero because the opposite forces are almost equal and cancel one another. Since the horizontal net force is close to zero horizontally, it does not accelerate the 1 kg appreciably in the horizontal direction.
The forces acting vertically are not equal because planet earth blocked some of the force coming from the other side of earth. The force directed downward is greater that the force directed upward. The result is close to 9.8 N per kg, depending on location on earth. It could be rounded to 10 N/kg for simplicity.
That means the 1 kg will go down at an average speed of 5 m/s until it falls to the ground.
Since the object is moving east at 340 m/s and the acting force of gravity is at 90 degrees compare to that speed, it has no acceleration effect in horizontal direction.
The speed directed downward increases in relation to the ground. Really, the ground is also moving east.
The speed of the 1 kg is always 340 m / s towards the east because the earth rotates. If no force was exerted down, on the mass, it would have continued in a straight line away from the floor. The next drawing show what would happen if there was no downward forces on 1kg.
Compare to the ground there is an acceleration 9.8 m/s2 for the 1 kg falling to the ground. But the ground is also ‘going down’ relative to space and moving east. In reality, there is a change in direction of a moving object so that the object seems to fall on the ground. Relative to earth fix space, gravity did not increase the speed of the object. The acceleration due to gravity is a change of direction, not a change of speed. This applies to all matter in universe because matter is always moving slowly compare to the moving light.