2.2 
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Interactive Simulations   Position and displacement in one dimension    Displacement and position in two dimensions    Solve v=dx/dt for dt    Velocity, position, and time (basic version)    Velocity, position, and time (more advanced version)    Acceleration (basic version)    Acceleration (more advanced version)    Static equilibrium    Static equilibrium and the lever    Newton's second law (basic version)    Newton's second law (more advanced version)    Circular motion interactive simulation    Orbits of the planets and dwarf planets    Orbits simulation Interactive Calculators   Speed calculator    Velocity calculator    Acceleration calculator    Velocity in accelerated motion    Average velocity calculator    Hooke's law calculator    Torque calculator    Rotational equilibrium and torque    Newton's second law calculator    Momentum calculator    Angular velocity    Linear velocity and angular velocity    Centripetal acceleration    Centripetal force    Law of universal gravitation calculator
1 - Science of Physics
2 - Forces and Motion      Chapter 2 at a glance      2.1 - Motion      2.2 - Force, momentum, and Newton's laws      2.3 - Circular motion      2.4 - Solving harder physics problems      2.5 - Chapter review3 - Energy Transformations4 - Waves and Sound
5 - Electricity and Magnetism
6 - Light and Optics
7 - The Atom
8 - Linear Motion
9 - Vectors and Forces
10 - Forces
11 - Newton's Laws and Gravitation
12 - Circular Motion and Gravitation
13 - Torque and Static Equilibrium
14 - Momentum and Collisions
15 - Angular momentum
16 - Power and Machines
17 - Harmonic Motion
18 - Waves
19 - Sound
20 - Electricity
21 - Electric and Magnetic Fields
22 - Electromagnetism and Induction
23 - Light and Color
24 - Geometrical Optics
25 - Electromagnetic Radiation
26 - The Properties of Matter
27 - Thermodynamics and Heat Transfer
28 - The Atom
29 - The Quantum Theory
30 - TBD
31 - TBD
32 - TBD
33 - TBD
34 - TBD
35 - TBD
36 - TBD
37 - The atomic nucleus and radioactivity
38 - Nuclear reactions
39 - Relativity
40 - Particle physics and the standard model
41 - Electronics (semiconductors)
42 - Nuclear technology
43 - Lasers and photonics
44 - Metals, alloys and materials science
45 - Communications technology
46 - Buildings and structures
47 - Energy technology
48 - Biophysics
49 - Matter and Energy, Space and Time
50 - Energy Transformations
51 - Nanotechnology
52 - Website Videos
53 - ExtraStuff
55 - Modeling Motion, Friction, and Center of Mass
56 - Work and the Conservation of Energy
Newton's first law and friction
What is the first law? Newton's first law of motion says that an object at rest or in motion remains in its identical state of rest or motion unless acted upon by a net force. Since inertia is the property of mass that resists change in motion, the first law is sometimes referred to as the law of inertia.
Newton's first law
What does the first law mean? Most people intuitively know that an object at rest stays at rest without the action of a net force. However, the first law also says that an object in motion remains in the identical state of motion unless acted upon by a net force. In real life, objects in motion always slow down and eventually stop without pushing or pulling forces. They do not keep moving in their identical state of motion. How is this fact reconciled with the first law?
What is friction? The first law is not violated because there is another force present whenever motion occurs in the real world. That force is friction. Friction is a "catch-all" word used to describe any resistive force that is caused by motion and always acts to resist motion. When a box slides against the floor, the sliding motion between the box and the floor results in a friction force that acts on the box to slow it down. In the real world, all macroscopic motion creates friction forces. The reason you must push a box to keep it moving at constant speed is to counteract friction. In accordance with the first law, the box moves with constant velocity only when the net force is zero because your applied pushing force exactly cancels the force of friction.
Effect of friction when applying Newton's first law
How do I use the First Law? The first law tells you how to approach problems that involve forces and motion. If things are at rest, and stay at rest, then the first law requires that the net force must be zero. This means you can use the condition of equilibrium to find unknown forces. The same is true for situations of constant velocity. Constant velocity is a condition in force equilibrium. If the net force is not zero, then we have a new situation calling for the second law, which we will cover on the next page.
Test your knowledge William is trying to slide a crate across his room. If the force of friction is greater than the pushing force that William can generate, will the crate begin to slide? Show

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