Complete Concept Guide (100% Curriculum Coverage)
1. Universal Law of Gravitation
Every particle in the universe attracts every other particle with a force proportional to the product of their masses and inversely proportional to the square of the distance between them: $$\mathbf{F = G\frac{M \cdot m}{d^2}} \quad \left(G = 6.674 \times 10^{-11}\text{ N}\cdot\text{m}^2\text{/kg}^2\right)$$
2. Acceleration Due to Gravity ($g$) vs. Mass & Weight
On Earth's surface, all freely falling objects accelerate downward at $g \approx 9.8\text{ m/s}^2$ regardless of mass!
• Mass ($m$): Quantity of matter in an object; constant everywhere (kg).
• Weight ($W = mg$): Gravitational pull acting on mass (Newtons); on the Moon, $g_{\text{moon}} = \frac{1}{6}g_{\text{earth}}$, so your weight on the Moon is one-sixth!
3. Archimedes' Principle & Buoyancy
When an object is immersed in a fluid, it experiences an upward buoyant force equal to the weight of fluid displaced by the body. A steel ship floats because its hollow shape displaces a volume of water whose weight is greater than the total weight of the ship!
Check Your Understanding (Diagnostic Practice Questions)
Diagnostic questions testing core conceptual clarity. Answers are hidden initially — solve each problem first, then click to reveal the step-by-step verified solution.
1
What is the weight of an object on the surface of the Moon if its weight on Earth is 60 N?
Reveal Answer & Explanation
Answer: $\text{Weight on Moon} = \frac{1}{6} \times 60 = 10\text{ Newtons}$.
One-sixth of Earth weight.
2
Why does an iron nail sink in water while a massive steel ship floats?
Reveal Answer & Explanation
Answer: An iron nail is solid and displaces a tiny volume of water whose weight is less than the nail's weight. A hollow ship displaces a massive volume of water whose buoyant force easily balances the ship's weight.
Ship displaces water equal to its weight.
3
An object is thrown vertically upwards with a velocity of $49\text{ m/s}$. Calculate the maximum height reached. ($g = 9.8\text{ m/s}^2$).
Reveal Answer & Explanation
Answer: At peak $v = 0$. $v^2 = u^2 - 2gh \implies 0 = 49^2 - 2(9.8)h \implies 19.6h = 2401 \implies h = 122.5\text{ meters}$.
v^2 = u^2 - 2gh.
4
Distinguish between Mass and Weight.
Reveal Answer & Explanation
Answer: Mass is the scalar quantity of matter in a body, measured in kg and constant everywhere; Weight is the downward gravitational force acting on it ($W = mg$), measured in Newtons and varying with local $g$.
Constant mass vs variable gravitational weight.
5
What happens to the gravitational attraction between two objects if the distance between them is doubled?
Reveal Answer & Explanation
Answer: Force is inversely proportional to distance squared ($F \propto 1/d^2$). If distance is doubled, the force becomes one-fourth ($1/4$) of its original value.
Inversely proportional to distance squared.
Finished Studying This Chapter?
READY TO PRACTICE?
Timed CBT Practice Tests (Exam Simulator)
Put your concepts to the test with official curriculum-aligned Foundation and Advanced practice tests. Get instant accuracy scores, time metrics, and step-by-step verified explanations.
