lesson 8
Energy
SI unit: Joule (J)
scalar
law of conservation of energy
mechanical energy = potential energy + kinetic energy
Total Energy in the beginning = Total Energy in the end
PE1 + KE1 = PE2 + KE2
Kinetic energy (Linear)
energy of a moving object because of its motion
KE = 1/2 mv^2
m = mass [kg]
v = velocity [m/s]
KE = kinetic energy [J]
potential energy
potential energy is stored in the object
Gravitational potential energy
GPE = mgh
m = mass[kg]
g = gravitational acceleration [m/s^2] = 9.81m/s^2
h = height [m]
GPE = gravitational potential energy [J]
GPE is the energy of an object due to its position above Earth's surface
mgh = 1/2mv^2
elastic potential energy
energy stored as a result of applying force to deform an elastic object
EPE = 1/2kx^2
k = spring constant [N/m]
x = displacement of the spring from neutral position [m]
EPE = elastic potential energy [J]
conservation of Mechanical Energy:
KE1 + PE1 = KE2 + PE2
1/2mv^2[final] + 1/2k(change in s)[final] = 1/2mv^2[initial] +1/2k(change in s) [initial]
Multiple Spring
series
they have same force passing through them as each contributes to the total deflection
1/k total = 1/k1 + 1/k2 + 1/k3 + ... 1/kn
parallel
have same deflection and total force is split among them, for springs in parallel individual spring rates add directly
k total = k1 + k2 + k3 + ....+ kn