Energy And Work

Front 1

The difference between positive and negative work

Back 1

• positive: energy transferred to object due to force
• negative: energy transferred from object due to force

Front 2

What type of product of vectors is work?

Back 2

• A scalar product
  
• W = F . s = F . s cos⁡θ
• F . s cos⁡θ = component of F along s
  

Front 3

What is the work done by a variable force?

Back 3

• ∆W = F(j,average) ∆x
  
• total W = sum of all j increments
  
• integrate

Front 4

What is the work-and-kinetic-energy theorem for a variable force?

Back 4

Front 5

Power

Back 5

The rate at which work is done

Front 6

How is potential energy related to work?

Back 6

ΔU = −W

Front 7

What is the gradient of a potential energy curve?

Back 7

Force

Front 8

What are the 3 equilibrium points?

Back 8

• neutral: mechanical E = U → K = 0. no F acts on particle + particle doesn't move. U′′(x) = 0
• unstable: K = 0 precisely @ this point but even small displacement causes particle being pushed further away. U′′(x) < 0
  
• stable: K = 0 but any displacement causes restoring F pushing particle back to stable equilibrium point. U′′(x) > 0

Front 9

What does the conservation of energy state?

Back 9

• total energy can only change by amounts that are transferred to/from system
• for an isolated system, total energies can be related @ different instants without considering them at intermediate times