Chapter 5
{ work } (Gravitational) Potential
energy
Definition:
o the product of the Definition:
displacement and the o the energy an object
component of the force possesses due to its position
parallel to the displacement relative to a reference point
o Scalar quantity
p = mgh
o Measured in Joules (J)
o 1J = 1Nm o Ep = potential energy (J)
o M = mass (kg)
W = FΔxcosθ
o G = grav acc (9.8 m.s-2)
+ work → θ = 0 (cos0 = 1)
o H = height above zero level (m)
- Work → θ = 180 (cos180 = -1)
No work → θ = 90 (cos90 = 0) Kinetic energy
WORK ON A SLOPE Definition:
o the energy an object has as a
app
result of the object's motion
F app k = ½mv2
o Ek = kinetic energy (J)
o M = mass (kg)
o V2 = velocity (m.s-1)
Fg⊥ = 0 (bcz at 90 to W) Law of conservation of
Fg// = mgsinθ mechanical energy
WFapp = FappΔxcosθ (cos0) Definition:
WFfric = FfricΔxcosθ (cos180) o the total energy in a system
cannot be created nor
WFg// = mgsinβΔxcosθ destroyed; only transformed
Wnet = Wfapp + Wffric + Wfg// from one form to another
{ energy } o In absence of air resistance or
external forces, Em of object = k
o Scalar quantity
(Ep + Ek)i = (Ep + Ek)f
{ work } (Gravitational) Potential
energy
Definition:
o the product of the Definition:
displacement and the o the energy an object
component of the force possesses due to its position
parallel to the displacement relative to a reference point
o Scalar quantity
p = mgh
o Measured in Joules (J)
o 1J = 1Nm o Ep = potential energy (J)
o M = mass (kg)
W = FΔxcosθ
o G = grav acc (9.8 m.s-2)
+ work → θ = 0 (cos0 = 1)
o H = height above zero level (m)
- Work → θ = 180 (cos180 = -1)
No work → θ = 90 (cos90 = 0) Kinetic energy
WORK ON A SLOPE Definition:
o the energy an object has as a
app
result of the object's motion
F app k = ½mv2
o Ek = kinetic energy (J)
o M = mass (kg)
o V2 = velocity (m.s-1)
Fg⊥ = 0 (bcz at 90 to W) Law of conservation of
Fg// = mgsinθ mechanical energy
WFapp = FappΔxcosθ (cos0) Definition:
WFfric = FfricΔxcosθ (cos180) o the total energy in a system
cannot be created nor
WFg// = mgsinβΔxcosθ destroyed; only transformed
Wnet = Wfapp + Wffric + Wfg// from one form to another
{ energy } o In absence of air resistance or
external forces, Em of object = k
o Scalar quantity
(Ep + Ek)i = (Ep + Ek)f
