2.2 
Jump to Book CoverPrevious Page
Next Page

Videos:
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
Momentum
What is momentum? Momentum is a property of an object in motion, whether it is a person, car, truck, or space ship. A car traveling down the road has momentum; it requires force from the brakes to change its velocity. A big truck traveling at the same velocity has much more momentum, because it is more difficult to change its velocity. Momentum is a quantity that describes the tendency for an object in motion to remain in motion.
Calculating momentum The momentum of a moving object is its mass multiplied by its velocity. The higher an object's mass or velocity, the more momentum it has. A truck has more momentum than a car moving at the same speed because the truck has more mass. Similarly, a car has more momentum when it is moving fast on the highway than when it is traveling slowly on a city street.
Momentum calculator
(2.12) p → =m v →
p  = momentum (kg m/s)
m  = mass (kg)
v  = velocity (m/s)
Momentum
vector notation
Momentum is a vector quantity Momentum is the product of mass and velocity; since velocity is a vector quantity, momentum is therefore also a vector quantity. Momentum in one dimension can take on either positive or negative signs to indicate its direction. For example, a 10 kg ball moving at 2 m/s to the right has a momentum of +20 kg m/s and the same ball moving to the left has a momentum of –20 kg m/s. Momentum has units of mass multiplied by speed—or kilogram meters per second (kg m/s).
Positive and negative momentum
Why “p” for momentum? The symbol for momentum is a lower case p or vector p. Historically, momentum was identified with the persistence of an object to continue in its original speed and direction of motion. While we call it “momentum” today, Newton called “impetus” in 1760. Impetus is derived from the Latin word petere, which means to go toward.
Can different objects have the same momentum? Two different ways to have the same momentum Objects with different masses can have the same momentum. For example, a 1 kg object moving at 100 m/s has the same momentum as a 100 kg object moving at 1 m/s. Both have the same “persistence of motion” described by Newton. Because the momentum is the same, it also takes the same force exerted over the same amount of time to stop either ball even though the masses and velocities are very different.
Momentum and Newton's first law Momentum is a fundamental quantity in physics. In the quantum world, momentum is more fundamental than either mass or velocity taken separately. Newton's first law might be more accurately named the law of momentum, because it is really momentum that remains unchanged when the net force is zero.
Test your knowledge Which has more momentum, a 4,000 pound car traveling at 60 miles per hour or a 30,000 kg truck traveling at 1.5 meter per second? Show

78 Previous Page Next Page