When a body is dropped from a height H, it falls freely due to the force of gravity. This is according to the first law of motion which states that any body is in a state of rest or is in a state of uniform motion until it is acted upon by an external force. When the body is held at a height H above the surface of the earth, a force is exerted in the opposite direction to prevent it from falling. Then the body begins to fall under the natural force of gravity.
Is this motion uniform or, in other words, does the body cover equal distances in equal time intervals? No, the motion accelerates when the acceleration due to gravity equals 9.81 m / s * s. In other words, it will cover unequal distances in equal time intervals as the body approaches the surface of the earth.
Let’s apply Newton’s second law of motion to the falling object. At any point, the external force on the body is m * a. Here a is equal to the gravitational force of attraction and, therefore, is equal to g. So the downward pulling force is m * g.
Let’s calculate the time needed to reach the ground from height H.
The laws of motion are S = u * t * t + 0.5 * g * t * t – (1)
Here u is the initial velocity and is equal to 0.
S is the distance traveled or is equal to H.
H = 0.5 * g * t * to H = 4.9 t * t. This can also be derived using the law of conservation of energy. So, at any point during free fall, the potential energy equals the kinetic energy 0.5 * m * v * v = m * g * h. vo the velocity of the body after time t under an acceleration of g can be calculated as v = u + gt where u is the initial velocity. So when the body is dropped from a height h, the initial velocity is 0. Then v = gt. The application of the law of conservation of energy is 0.5 * m * g * g * t * t = m * g * h. So h is 0.5 * g * t * t. In fact, all equations of motion can be derived using the law of conservation of energy.
Therefore, the time it takes for a body to fall from a height of 49 meters is sqrt (10) seconds, to fall from a height of 100 meters is sqrt (20.4) or 4.51 seconds. Comparatively, the time it takes for a human to run through 100 m. It is 10 seconds, so one can imagine the extent of the natural force of gravity.
Using the same equation (1) you can calculate the distance traveled by a body, say half a minute. In half a minute or 30 seconds, a body will reach the earth’s surface from a height of 4410 meters or 4.4 km. It can also be seen that in 1 minute or 60 seconds a body can fall from a height of 17,640 meters or 17.64 kilometers. It can also be immediately verified that the body does not travel equal distances in equal time intervals.
Another interesting aspect of free fall is that the equations of motion are independent of mass. But mass can affect movement if there is resistance due to the wind and if the surface of the body is not uniform. This can cause upward drag and movement may not be uniform for all masses. But without air resistance or in a vacuum, the movement will be as described above.