This is a summary for things you need to know under gravitation and orbital motion. It includes the following:
- Important definitions regarding circular motion
- Important derivations including centripetal force, tangential velocity, angular velocity, etc...
- Universal law of gravitation
• Radian: When arc length is equal to the radial length, the angel subtended at the centre of
the circle is a radian.
• Angular speed (ω): This is the rate of change of angular displacement (θ). It is measured
in rads-1.
• Centripetal force(Fc): Force associated with objects moving in a circular motion; it is
directed towards the centre.
Figure 1
Important formulae and relationships
• Tangential speed(v): The linear speed of an object moving in a circular motion.
𝑣 = 𝜔𝑟
Figure 2
• Centripetal acceleration(a): This is the acceleration caused by an object moving in a
circular motion, it is always directed towards the centre of the circle.
𝑎 = 𝜔2 𝑟
• Period(T): This is the time taken to complete one full rotation, i.e., 360ᵒ or 2π radians
Relationship between vt, ω, and T.
1. v,ω and r
𝑣 = 𝜔𝑟
𝜔 = 𝑣𝑟
, 𝑎 = 𝜔2 𝑟
𝑣2
𝑎= ⋅𝛾
𝑟2
𝑣2
𝑎=
𝑟
2. Fc, a, ω and v
𝐹𝑐 = 𝑚𝑎
𝑎 = 𝜔2 𝑟 𝑜𝑟 𝑎 = 𝜔2 𝑟
𝑚𝑣 2
𝐹𝑐 = 𝑚𝜔2 𝑟 𝑜𝑟 𝐹𝐶 =
𝑟
3. T and ω
2𝜋
𝑇=
𝜔
Gravitation
The universal law of gravitation:
“In the universe, every object attracts every other object with a force that is directly proportional
to the product of the masses of the objects, and indirectly proportional to the square of the
distance between them.”
Figure 3
From the law:
𝐹 ∝ m1 m2
1
𝐹∝
𝑟2
𝑚1 𝑚2
𝐹∝
𝑟2
𝐺𝑚1 𝑚2
𝐹=
𝑟2
Where G is the universal gravitational constant. It has the value: 𝐺 = 6.67 × 10−11 𝑁𝑚2 𝑘𝑔−2 .
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
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 EFT, 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 this summary from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller rndmstudent. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy this summary for R65,03. You're not tied to anything after your purchase.