# What is the value of gravity in free-fall and two-dimensional kinematics?

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In summary, when an object is in freefall on Earth, gravity is always 9.8m/s^2 down. In 2D, the gravity is also down on the object regardless of its motion.
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## Homework Statement

I have just a question to clarify. When an object is in free-fall the gravity is always + 9.81 m/s^2? and also when it is talking about two dimension kinematics gravity is working on an object thrown in the air it is -9.81 m/s^2?

## The Attempt at a Solution

Yes, when the object is in freefall on Earth, gravity = a = 9.8m/s^2 down. Signs are optional but you could say -9.8n/s^s.
In 2D, the gravity is always 9.8m/s^2 down on the object.

It doesn't matter how the object is moving or thrown, gravity is always down.

The acceleration due to gravity, denoted as g, is a constant value of 9.81 m/s^2 near the Earth's surface. This value is always positive and acts in the downward direction, regardless of the motion of the object. In the case of free-fall, where an object is only under the influence of gravity, the acceleration will always be equal to g.

In two-dimensional kinematics, the acceleration due to gravity will still be equal to g, but it may act in different directions depending on the motion of the object. For example, if an object is thrown upwards, the acceleration due to gravity will be acting in the downward direction, causing the object to slow down. This is why it is often written as -9.81 m/s^2 in equations, to indicate that it is acting in the opposite direction of the object's motion. However, the magnitude of the acceleration is still 9.81 m/s^2.

It is important to note that the value of g may vary slightly depending on the location and altitude, but for most practical purposes, it can be considered a constant value of 9.81 m/s^2 near the Earth's surface. I hope this clarifies your question.

## 1. How is free-fall different from normal gravity?

Free-fall is the motion of an object towards the ground due to the force of gravity, while normal gravity refers to the constant force of attraction between two objects with mass. In free-fall, the only force acting on the object is gravity, whereas in normal gravity, other forces such as air resistance may also be present.

## 2. What is the acceleration of an object in free-fall?

The acceleration of an object in free-fall is always constant and equal to the acceleration due to gravity, which is approximately 9.8 meters per second squared. This means that the object's velocity will increase by 9.8 meters per second every second as it falls.

## 3. How does mass affect free-fall acceleration?

The mass of an object does not affect its acceleration in free-fall. All objects, regardless of their mass, will fall towards the ground at the same rate of 9.8 meters per second squared. This is often referred to as the universality of free-fall.

## 4. What factors can affect the speed of an object in free-fall?

The speed of an object in free-fall is affected by several factors, including the object's initial velocity, air resistance, and gravitational pull. Objects with a higher initial velocity or a larger surface area for air resistance will fall slower than objects with a lower initial velocity or smaller surface area.

## 5. Can an object reach terminal velocity in free-fall?

Yes, an object can reach terminal velocity in free-fall. Terminal velocity is the maximum speed an object can reach when falling through a fluid, such as air. When an object reaches terminal velocity, the force of air resistance is equal to the force of gravity, resulting in a constant speed with no further acceleration.

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