# Newton's law conceptual question

• riverjib
In summary, the forces between the Earth and an individual are equal and opposite based on Newton's third law. Additionally, the water level in a glass of water will not rise when an ice cube, which has the same density and volume as water, melts. This is due to the law of displacement, which states that the water displaced by the ice cube equals the volume of the ice cube.

#### riverjib

1. Homework Statement [/b]
The force you exert on the Earth is insignificant compared to the force the Earth exerts on you. (True or false)

The attempt at a solution[/b]

I believe that this is false based upon Newton's third law--shouldn't the forces be equal and opposite?

2. Ice cube floating in glass of water--water level increases when it melts.

Is this also false? Unless the ice cube is being held under the water, shouldn't the density and volume differences cancel out since the mass does not change? (Assuming the ice is chemically identical to the water?)

I believe that this is false based upon Newton's third law--shouldn't the forces be equal and opposite?

I believe You're right.

about the second question , I don't want to say something wrong, so You'll have to wait some 1 else .
but I think you're right here as well

You are right at 2, too. At yes, that is the right way of thinking.

Thank you both!

Welcome to PF!

Hi riverjib! Welcome to PF!
riverjib said:
The force you exert on the Earth is insignificant compared to the force the Earth exerts on you. (True or false)

I believe that this is false based upon Newton's third law--shouldn't the forces be equal and opposite?

Yup!
Ice cube floating in glass of water--water level increases when it melts.

Is this also false? Unless the ice cube is being held under the water, shouldn't the density and volume differences cancel out since the mass does not change? (Assuming the ice is chemically identical to the water?)

Yup again!

(but mention the law specifically: water displaced equals … ?)

That's why sea-level doesn't rise when floating ice in Antarctica melts.

Thanks Tim
I'm glad I found this forum!

## 1. What are Newton's laws of motion?

Newton's laws of motion are three fundamental laws that describe the relationship between an object's motion and the forces acting upon it. They were developed by Sir Isaac Newton in the 17th century and are considered the foundation of classical mechanics.

## 2. What is the first law of motion?

The first law of motion, also known as the law of inertia, states that an object will remain at rest or in motion with a constant velocity unless acted upon by an external force. In other words, objects tend to resist changes in their motion.

## 3. What is the second law of motion?

The second law of motion states that the acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass. In simpler terms, the greater the force applied to an object, the greater its acceleration will be. Similarly, the more massive an object is, the less it will accelerate for a given force.

## 4. What is the third law of motion?

The third law of motion, also known as the law of action and reaction, states that for every action, there is an equal and opposite reaction. This means that when an object exerts a force on another object, the second object will exert an equal and opposite force back on the first object.

## 5. How do Newton's laws apply in everyday life?

Newton's laws of motion can be observed in many everyday situations, such as when a car accelerates or when a person jumps. They also play a crucial role in the design and functioning of various machines and technologies, such as airplanes and rockets. Understanding these laws can help us better understand and predict the behavior of objects in our surroundings.