Case Study 1: Universal Law of Gravitation
Isaac Newton observed an apple falling from a tree and proposed that every object in the universe attracts every other object with a force which is directly proportional to the product of their masses and inversely proportional to the square of the distance between them.
Questions:
- Force of gravitation is proportional to:
(a) m₁ + m₂ (b) m₁ × m₂ (c) m₁ – m₂ (d) none
Answer: (b) - Force of gravitation ∝ 1/(distance)² is called:
(a) inverse law (b) inverse square law (c) direct law (d) none
Answer: (b) - Gravitational constant (G) = ?
(a) 9.8 m/s² (b) 6.67 × 10⁻¹¹ Nm²/kg² (c) 6.67 × 10⁻¹¹ J/kg (d) none
Answer: (b) - Force becomes zero if:
(a) mass = 0 (b) distance = ∞ (c) both (d) none
Answer: (c) - Earth attracts apple due to:
(a) electromagnetism (b) gravitation (c) nuclear force (d) none
Answer: (b)
Case Study 2: Free Fall
A ball dropped from a height falls towards the Earth due to gravity. It accelerates uniformly at 9.8 m/s².
Questions:
- The acceleration in free fall = ?
(a) 0 (b) g (c) G (d) none
Answer: (b) - Value of g on Earth = ?
(a) 9.8 m/s² (b) 6.67 × 10⁻¹¹ (c) 10 N/kg (d) 8.9 m/s²
Answer: (a) - The motion is:
(a) uniform motion (b) uniformly accelerated (c) retarded (d) none
Answer: (b) - If air resistance is absent, all bodies fall with:
(a) same acceleration (b) different acceleration (c) zero acceleration (d) none
Answer: (a) - Free fall is an example of:
(a) non-uniform motion (b) uniformly accelerated motion (c) zero force (d) none
Answer: (b)
Case Study 3: Mass and Weight
Rohit measured his mass on Earth and Moon. His mass was the same on both, but his weight was one-sixth on the Moon compared to Earth.
Questions:
- Mass depends on:
(a) location (b) gravity (c) amount of matter (d) none
Answer: (c) - Weight depends on:
(a) mass only (b) gravity only (c) both (d) none
Answer: (c) - W = ?
(a) mg (b) ma (c) mv (d) none
Answer: (a) - On Moon, g = ?
(a) 9.8 m/s² (b) 1.63 m/s² (c) 4.9 m/s² (d) 19.6 m/s²
Answer: (b) - If a boy’s mass = 60 kg, weight on Earth = ?
(a) 600 N (b) 588 N (c) 100 N (d) 980 N
Answer: (b)
Case Study 4: Weightlessness in Satellites
Astronauts inside a satellite feel weightless because both they and the satellite fall freely under Earth’s gravity.
Questions:
- Weightlessness occurs when:
(a) gravity is zero (b) normal force is zero (c) both (d) none
Answer: (b) - Weightlessness in satellite is due to:
(a) no gravity (b) free fall (c) zero mass (d) none
Answer: (b) - Apparent weight inside satellite = ?
(a) 0 (b) infinite (c) finite (d) none
Answer: (a) - Real weight in satellite = ?
(a) zero (b) same as on Earth (c) double (d) none
Answer: (b) - Free fall path of satellite is called:
(a) linear motion (b) orbital motion (c) random motion (d) none
Answer: (b)
Case Study 5: Thrust and Pressure
A girl wearing sharp-heeled shoes exerts more pressure than when wearing flat shoes because pressure depends on force per unit area.
Questions:
- Pressure = ?
(a) Force × Area (b) Force/Area (c) Area/Force (d) none
Answer: (b) - If area decreases, pressure:
(a) decreases (b) increases (c) remains constant (d) none
Answer: (b) - SI unit of pressure:
(a) N (b) Nm² (c) Pa (d) J
Answer: (c) - Wearing heels exerts:
(a) less pressure (b) more pressure (c) no pressure (d) none
Answer: (b) - Pressure depends on:
(a) force only (b) area only (c) both (d) none
Answer: (c)
Case Study 6: Buoyancy
Ramesh placed a stone in water. It displaced some water and appeared lighter inside water than in air.
Questions:
- Upward force by fluid = ?
(a) weight (b) thrust (c) buoyant force (d) none
Answer: (c) - Buoyant force depends on:
(a) weight of body (b) weight of displaced fluid (c) volume of body only (d) none
Answer: (b) - If weight of body < buoyant force, body:
(a) sinks (b) floats (c) dissolves (d) none
Answer: (b) - If weight of body > buoyant force, body:
(a) sinks (b) floats (c) rises (d) none
Answer: (a) - Buoyant force is exerted by:
(a) solid (b) liquid/gas (c) both (d) none
Answer: (b)
Case Study 7: Archimedes’ Principle
A goldsmith dipped a crown into water and found it displaced more water than expected, proving it was mixed with silver.
Questions:
- Archimedes’ principle states:
(a) body experiences upward force equal to weight of liquid displaced (b) equal to volume of liquid displaced (c) equal to density of liquid (d) none
Answer: (a) - Principle used in:
(a) hydrometer (b) ship design (c) submarine (d) all
Answer: (d) - Crown was impure because:
(a) displaced less water (b) displaced more water than pure gold (c) did not displace (d) none
Answer: (b) - Archimedes’ principle is related to:
(a) density (b) buoyancy (c) both (d) none
Answer: (c) - SI unit of density = ?
(a) kg/m³ (b) N/m² (c) J/m³ (d) Pa
Answer: (a)
Case Study 8: Floating and Sinking
An iron nail sinks in water, but a big iron ship floats.
Questions:
- Nail sinks because:
(a) density > water (b) density < water (c) buoyant force greater (d) none
Answer: (a) - Ship floats because:
(a) density < water due to hollow shape (b) density > water (c) weight = 0 (d) none
Answer: (a) - Floating depends on:
(a) shape (b) average density (c) buoyant force (d) all
Answer: (d) - Condition for float:
(a) density body < density fluid (b) density body > density fluid (c) equal (d) none
Answer: (a) - Submarines float/sink by:
(a) changing volume (b) changing mass (c) changing density with ballast tanks (d) none
Answer: (c)
Case Study 9: Fluids and Atmospheric Pressure
When we drink juice using a straw, we suck air out of the straw. Atmospheric pressure pushes the liquid upward.
Questions:
- Reason liquid rises in straw = ?
(a) gravity (b) muscular force (c) atmospheric pressure (d) none
Answer: (c) - Pressure of air decreases when:
(a) we suck (b) we blow (c) we press (d) none
Answer: (a) - Value of standard atmospheric pressure:
(a) 10⁵ Pa (b) 10³ Pa (c) 10² Pa (d) 10⁴ Pa
Answer: (a) - Mercury rises in barometer because of:
(a) gravity (b) atmospheric pressure (c) buoyancy (d) none
Answer: (b) - Application of atmospheric pressure:
(a) syringes (b) vacuum packs (c) suction pumps (d) all
Answer: (d)
Case Study 10: Density Applications
Oil floats on water because its density is less. Icebergs float with a large portion submerged.
Questions:
- Oil floats because:
(a) density < water (b) density > water (c) equal density (d) none
Answer: (a) - Ice density = ?
(a) less than water (b) more than water (c) equal (d) none
Answer: (a) - Fraction submerged of iceberg = ?
(a) 1/2 (b) 1/3 (c) 9/10 (d) 1
Answer: (c) - Density formula = ?
(a) mass/volume (b) volume/mass (c) mass × volume (d) none
Answer: (a) - SI unit of density = ?
(a) N/m² (b) kg/m³ (c) J/kg (d) Pa
Answer: (b)