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# The Physics of Falling Objects

This lesson aligns with Next Generation Science Standards (NGSS) PS2.C

Introduction
The falling of objects is a phenomenon that has captivated humans for centuries. From the ancient Greeks who thought about the nature of gravity, to modern physicists who study the laws that govern it, the physics of falling is a fascinating topic that has been the subject of much research and explanation. If someone drops two objects; one heavy, and one light from the same height, which one will hit the floor first? Most people instinctively pick the heavier one. And why wouldn’t they? after all, stones fall faster than feathers. In this article, we will explore the physics of falling objects, the force that causes objects to fall, and the factors that influence the speed and trajectory.

Gravity: The Force Behind Falling
The most remarkable fact about falling objects is gravity which causes an object to fall toward the earth. Gravity is a force of attraction that attracts a body toward the center of the earth or any physical body having mass causing them to accelerate downwards. The magnitude of the force of gravity depends on the mass of the objects and the distance between them.

Acceleration due to Gravity
The acceleration due to gravity is a constant rate at which objects fall toward the earth. On the surface of the earth, this value is approximately 9.8 m/s2. For every second an object falls toward earth, its speed increases by 9.8 m/s. The acceleration due to gravity is the same for all the falling objects, regardless of their mass and size. Objects with more mass have more gravity and the closer the objects are to each other, the stronger their gravitational pull is.

Gravity in the Universe
Gravity plays a fundamental role in sustaining life on earth. For instance, gravity holds the planets in orbit around the sun and it is also the main reason that keeps the moon in orbit around earth. The gravitational pull also affects the seawater causing the ocean tides. The gravity of the sun keeps the earth around it, keeping us at a comfortable distance so that we can enjoy the sun’s light and warmth.

Factors Affecting the Falling Objects
The speed and path of a falling object are affected by several factors. The most significant factors are air resistance and the initial velocity of the falling object.

Air Resistance
Air resistance is a force that occurs due to air when the object moves through it. This force opposes the motion of the falling object and always acts in the opposite direction to a body passing through the air. As an object falls, it encounters air molecules that push back against it by exerting frictional force on it. The magnitude of air resistance depends on the size, shape, and velocity of the object. Objects with a larger surface area experience more air friction than objects with a smaller surface area. Similarly, objects with less streamlined shape experiences more air friction than objects with a more streamlined shape.

Initial Velocity
The initial velocity refers to the speed of the falling object and the direction of motion at the moment it starts to fall. Objects that are dropped from a lower altitude have a lower initial velocity than objects that are dropped from a higher altitude. The path of the object that is determined by the initial velocity is known as trajectory. If this initial velocity is horizontal, the object will follow a curved path known as projectile motion.

Terminal Velocity
Terminal velocity refers to the maximum speed attained by a falling object due to the balance between the force of gravity and air resistance. When an object begins to fall, its speed increases as the force of gravity pulls it toward the ground. As the object falls faster, more air friction encounters, eventually reaching a point where it balances out the force of gravity. At this point, the object reaches terminal velocity and then falls at a constant speed until it reaches the ground.

Summary
• The physics of falling objects is a fascinating topic that helps us understand the behavior of objects in motion.
• Gravity is the force that causes objects to fall and the acceleration due to gravity is a constant value at which objects fall toward the earth.
• Air resistance and initial velocity are the major factors that affect the speed and trajectory of falling objects.

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