Chapter 7 & 8 Energy and Conservation Law
Work and Power2. Kinetic Energy & Work- Energy Principle3. Conservative and Nonconservative Forces4. Potential Energy5. Conservation of Energy
7-1  Work and Power (P147-)
Work is a scalar quantity, no direction.
positive work;
质点受力与它位移标积
zero work;
negative work.
Explanations:
(1) If the force is constant in the whole path,
(2) Work done by a variable force: