Physics- Work

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Equation of Work

W=F„d = (Fcosθ)d
Define Work

Scalar
Work is positive if

the force, or a component of force, acts in the same direction as the displacement
Work is negative if

a force, or a component of force, acts in the opposite direction of displacement
No work if

force is perpendicular to displacement, or if there is no displacement
cos 0

1
cos 90

0
cos 180

-1
Formula or stretching or compressing a string

W=½kx²
Formula for Kinetic Energy

K=½mv²
Formula for Potiental Energy: Spring

U_s=½kx²
Formula for Potiental Energy: Gravitational

U_g=mgy
Formula of Conserved Energy
- E₀=E
- K₀+U₀= K+U
What conserves energy?

Spring and Gravity
What does not conserve energy? (Nonconservative)

Friction
Formula of Total Energy
- E₀+W_nc=E
- K₀+U₀+W_nc=K+U
Steps for solving energy problems
- 1) Draw Diagram
- 2) Indicate Initial and Final Position
- 3) Indicate where gravitational poteintal energy is zero
- 4) Use E₀+W_nc=E
Formula of Power

P=Work/Time
Units of Power
- (W) Watt
- 1 J/S = 1 W
- I hp = 746 W
Units of Work
- J (Joule)
- 1 N*M = I J
Formula of Efficiency

E = W_out/E_in
Formula for Linear Momentum

P=mv