Peoples Physics Book Version-3

http://www.ck12.org Chapter 1. Units and Problem Solving

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• Vectors can be added together in a simple way. Two vectors can be moved (without changing their directions)
  to become two legs of a parallelogram. The sum of two vectors is simply the diagonal of the parallelogram:

Key Equations

1 meter= 3 .28 feet

1 mile= 1 .61 kilometers

1 lb. (1 pound)= 4 .45 Newtons

Key Applications

The late great physicist Enrico Fermi used to solve problems by making educated guesses. Say you want to
guesstimate the number of cans of soda drunk in San Francisco in one year. You’ll come pretty close if you guess
that there are about 800,000 people in S.F. and that one person drinks on average about 100 cans per year. So, around
80,000,000 cans are consumed every year. Sure, this answer is not exactly right, but it is likely not off by more than
a factor of 10 (i.e., an “order of magnitude”). That is, even though we guessed, we’re going to be in theballparkof
the right answer. This is often the first step in working out a physics problem.

TABLE1.1:

Type of measurement Commonly used symbols Fundamental units

length or position d,x,L meters(m)

time t seconds(s)

velocity or speed v,u meters per second(m/s)

mass m kilograms(kg)

force F Newtons(N)

energy E,K,U,Q Joules(J)

power P Watts(W)

electric charge q,e Coulombs(C)

temperature T Kelvin(K)

electric current I Amperes(A)

electric field E Newtons per Coulomb(N/C)

magnetic field B Tesla(T)

magnetic flux Φ Webers(W b)