2.4 
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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
2.4 - Solving harder physics problems
Problems in physics usually give you some information and ask you to use physics relationships you know to figure out something else. Solving problems teaches you to analyze information and think logically about how to get an answer. This section goes through a more difficult example that shows how to analyze a problem that seems simple, but is more complicated than it looks.
How to start
How do I start a problem? Question posed for two bicyclists approaching each other on a road One of the most difficult steps in beginning a physics problem is how to start. Starting often means translating from diagrams and words into the language of math. Mathematics is a language and part of beginning any physics problem is translating the words into:
  1. what the problem is asking for and,
  2. what information you are given or know.

What does the problem ask you to find?
What is the first thing to look for? The last sentence of the example problem tells you what the answer should be. "How long will it be before ..." is a reference to time. This problem asks you to find a time. Choose a variable to represent time. The letter, t, is a good choice. Mathematically, you are seeking a solution to the equation t = ?
How do I organize my information? Setting the variables for the distance and two velocities In this problem we are given two speeds and a distance. Because there are two speeds, we cannot use the same letter v, for both. When there is more than one of the same type of variable a good strategy is to use subscripts. Make one bicycle “number 1” and the other “number 2.” The velocity of bicycle number one is v1 (say “vee one”). The velocity of bicycle two is v2. These are different variables but they are both velocities.
How do I connect what I know and what I am given? Write down all the relationships you know that involve the types of information you are asked and given. For this problem you are asked for a time. You are given speeds and a distance. The relationship you need is one that relates speed, distance, and time. This relationship is v = d ÷ t.
Extracting the physics information from the wording of the question
Test your knowledge A net force of 100 N acts on a cart with a mass of 5 kilograms. Determine the acceleration of the cart if the cart is free to move with no friction.
Which of the following relationships is the most useful in solving this problem, involving what is asked and what is given?
  1. a = F ÷ m
  2. Fnet = F1 + F1 + F1 + ...
  3. v = v0 + at
  4. τ = F × d
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