WEP Flashcards
1
Q
Defn of energy
A
Energy is the capacity to do work
2
Q
GPE aka … & eqn
A
aka WD against gravity = mgh
3
Q
Eqn for elastic potential energy
A
1/2 kx^2
4
Q
Eqn for KE
A
1/2 mv^2
5
Q
Power eqn
A
P = dw / dt = d (Fs) / dt = F ds / dt = Fv
6
Q
Efficiency eqn
A
n = Pout / Pin X 100% = Eout / Ein X 100%
7
Q
Principle of COE - eqn
A
Total Ei = Total Ef
KEi + GPEi + EPEi + Wforce (any force) = KEf + GPEf + EPEf + Wfriction
8
Q
How to draw the E - s graph for EPE, GPE & KE
A
GPE is linear
EPE is exponential
KE = sad face
9
Q
Try speed boat eg in notes
A
Total P = Fv = kv^2 . v = kv^3 24000 X 3 = k (12)^3 k = 41.67 Next, when only 2 engines are working 24000 X 2 = 41.6 v^3 v = 10.5 m/s
10
Q
How to find wk done from 2 graphs
A
Are under
F - s graph &
P - V graph
