2.2 
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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 second law
What is the Second Law? Newton's second law of motion is probably the most widely used equation in all of physics. It says the acceleration of an object is equal to the force you apply divided by the mass of the object. If you apply more force to an object, it accelerates at a higher rate. For a given force, an object with more mass will accelerate less. If the net force is zero then the acceleration is also zero which means no change in speed or direction. The first law is therefore a special case of the second law, when a = 0.
Newton's second law calculator
(2.11) a= F m
F  = Net force (N)
m  = mass (kg)
a  = acceleration (m/s2)
Newton's second law
acceleration version
How do I use the Second Law? Some ways to use Newton's second law The second law is most often used in the following three ways.
  1. To determine the acceleration of an object from the net force.
  2. In the form F = ma to determine the net forces acting on an object from its observed or given acceleration.
  3. In the form F = ma to determine what net force must be applied to achieve a desired acceleration.
Problems involving position or velocity In many problems the force and mass may be known but the desired answer is not the acceleration, but instead is a speed or position. Solving these kinds of problems tends to proceed in two steps.
  1. Use the second law to determine the acceleration.
  2. Use the acceleration to determine the speed and position. This usually requires knowing the initial values of speed and position.
Units and the second law One newton equals one kilogram times one meter per second per second (m/s2). When using the Second Law you must be sure to convert all information into consistent units. Speeds must be converted to m/s. Masses in grams should be converted to kilograms and forces in pounds should be converted to newtons.
Test your knowledge Simone is pushing a cart that weighs 25 kg. She pushes with a force of 100 N. What is acceleration of the cart?
  1. 0.25 m/s2
  2. 0.4 m/s2
  3. 4 m/s2
  4. 2,500 m/s2
    5. Show
Solved Problem 2.5: Calculating Force from acceleration and mass
A regulation soccer ball with a mass of 450 grams starts at rest and is kicked with an acceleration of 80 m/s2. This means the ball leaves the players foot at a speed of 8 m/s after being in contact for 0.1 seconds. Calculate the force the player's foot exerts on the ball.

Asked: You are asked to calculate the force.
Given: m = 0.45 kg, v = 8 m/s, t = 0.1 s, a = 80 m/s2
Relationships: F = ma
Solution: Much of the information is not needed since you are given mass and acceleration.
The force is F = ma = (0.45 kg)(80 m/s2) = 36 N
Since the ball weighs 4.4 N, this force is 8 times as large as the ball's weight.
Answer: 36 N

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