Grade 12 Physical Sciences (Term 2) Summaries. These summaries are composed using the Platinum textbooks' work with examples and supplementary notes.
A) Topic 4:
* Chapter 6: Work, Energy and Power.
B) Topic 5:
* Chapter 7: The Doppler Effect.
C) Topic 6:
* Chapter 8: R...
Conservation of Mechanical U4: Power:
Energy with Only Scientific Meaning of Power:
Conservative Forces Present:
• Power – scalar – measured in watts.
W E
• Law of conservation of energy: Energy cannot be • P = t or P = t .
created or destroyed, but one form of energy can • Calculating total energy from power: W = P x t
be transformed into an equivalent amount of or W = E x t.
another form.
• In closed system – sum of Ep and Ek remain
constant.
• Net external force acting on system = 0.
• Only conservative forces exist if mechanical energy
Average Power Required to Keep
Sample
conserved.
• Law of conservation of mechanical energy: Total Object Moving Across Rough Surface:
Em (sum of gravitational Ep and Ek) in closed system U3: Conservation
remains constant. • Pav = Fvav.
• Sum of Ep and Ek remains constant during free fall.
of Energy (B) • Power rating on electric machines indicates rate at
• Ep at top = Ek at bottom. which they do work.
U4: Power
Summaries after sample
work done 𝐹∆𝑥 𝑚𝑔 x ℎ
• Power = time taken = 𝑡 = 𝑡
•
Conservation of Energy with Non-
Conservative Forces Present: Mechanical Energy in Absence of
• Don’t conserve mechanical energy. Non-Conservative Forces:
• Energy gained or lost due to dissipative forces.
• Wnet = Wc + Wnc • ΔEk = -ΔEp
• Wnc = ΔEk + ΔEp • Kinetic energy gained = potential energy lost
without conservative forces.
• Sum of Ek and Ep constant.
• Produced through various polymerisation
reactions.
, U1: Definition of Work:
• Work done on object when
force is exerted on the object,
and it moves in direction of
force. Net Work Done on Object:
• W = F x ∆𝑥 x cos θ
• Work – scalar. • When more than 1 force acts on an object – W done is
• SI unit for work – Newton-metre the sum of all the W done by each force in direction of
called the joule. motion.
U1: Definition
of Work
Positive and Negative Work:
• Positive work – F in direction of motion – increasing
Instances in Which Work is or isn’t Done: system’s energy.
• Negative work – F in opposite direction to motion –
• Work only being done when force acts on object and decreasing system’s energy.
object moves in direction of force. • Forces exerted at right-angle to motion or no
• If force exerted at angle to direction of motion – only the motion – no W done.
component of force parallel to direction of motion does • Forces exerted at angle to direction of motion –
work. only F parallel to direction of motion does work.
• Work done in lifting objects: W = mg x h
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card or Stuvia-credit for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller SummariesSA. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for $8.61. You're not tied to anything after your purchase.
