Work, Energy & Power

Question 1

Forms of Gravitational Equilibrium

Answer 1

Neutral: Gravitational Potential Energy in relation to position is constant.
Stable: Changing position increases Ug, provoking a gravitational restorative force.
Unstable: Changing position decreases Ug, provoking a gravitational non-restorative force.

Question 2

Work, Constant and Non-constant Force

Answer 2

Units are J, or N*m. Scalar.

Constant: W=F vec dot delta r vec, or F delta r cos theta.
Non Constant: Int x int to xf (Force, dx).

Question 3

Hooke’s Law

Answer 3

Spring Force = -Kx. For spring energy, 1/2 k(x int - x final)^2

Question 4

Kinetic Energy

Answer 4

1/2 Mv^2

Question 5

Gravitational Energy, Non-universal

Answer 5

Mgh

Question 6

Conservation of Energy, Isolated & Non-Isolated

Answer 6

Isolated: System Energy is conserved, delta ME = W non con
Non-Isolated: Change in System E = delta energy transfer, or delta ME + W non con.

Question 7

Power to Energy to Work.

Answer 7

Power is dE/dt, J/s or watts. Associated with Fv. dw = P dt, or delta W = int time inital to time final (P dt). Work is just delta E. In other words, Power is Work over Change in Time, or Change in Energy over Change in Time.

P/t = delta W.

Question 8

Conservative Force

Answer 8

Path independent. F = - derivative of energy with respect to position. Why force of a spring relates to spring energy