Normal force and contact force | Forces and Newton's laws of motion | Physics | Khan Academy | Summary and Q&A

TL;DR

Newton's First Law states that an object at rest or in motion will remain that way unless acted upon by a net force. The normal force, provided by a surface, balances out the force of gravity to keep objects stationary or in constant motion.

Key Insights

• 🧑‍🏭 Newton's First Law states that objects maintain their state of motion unless acted upon by a net force.
• 🍂 The normal force is an upward force exerted by surfaces, preventing objects from falling or accelerating downwards.
• ❓ Without the normal force, objects would accelerate towards the center of the Earth due to the force of gravity.
• 🫀 The normal force depends on electromagnetic repulsion between the atoms or molecules of objects and their supporting surfaces.
• ❓ In future studies, the normal force will become essential when considering friction and inclined surfaces.
• 🤪 The normal force is perpendicular to the supporting surface and prevents objects from going through solid materials.
• ❓ Objects on inclines experience a normal force that counteracts the force component pulling them down the incline.

Transcript

Let's say that I have a huge, maybe frozen over lake, or maybe it's a big pond. So I have a huge surface of ice over here-- my best attempt to draw a flat surface of ice-- and I'm going to put two blocks of ice here. So I'm going to put one block of ice just like this, one block of ice right over here. And then I'm going to put another block of ice... Read More

Questions & Answers

Q: What does Newton's First Law of Motion state?

Newton's First Law states that objects at rest will remain at rest, and objects in motion will continue moving at a constant velocity unless acted upon by an unbalanced force.

Q: What force counteracts the force of gravity to keep objects from falling?

The normal force, provided by a supporting surface, counteracts the force of gravity and prevents objects from accelerating downward.

Q: Why does a block of ice on a frozen pond experience a normal force?

The normal force is the result of electromagnetic repulsion between the atoms or molecules of the block of ice and the surface of the pond, preventing the block from sinking further.

Q: How does the normal force play a role in objects on inclined surfaces?

The normal force acts perpendicular to the surface and helps balance out the force component pushing the object down the incline, influencing the object's motion.

Summary & Key Takeaways

• Newton's First Law states that an object will maintain its state of rest or constant velocity unless acted upon by a net force.

• The force of gravity, exerted on objects near Earth's surface, pulls them downwards with a force equal to mass multiplied by the gravitational field strength (9.8 m/s^2).

• The normal force is the upward force exerted by a surface, which counteracts the force of gravity, allowing objects to stay stationary or move with a constant velocity.