Assertion (A): When ice floats in water, its approximately 1/10th volume remains outside the water. Reason (R): The density of ice is approximately 10% less than the density of water. MCQ with Answer and Explanation

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Assertion (A): When ice floats in water, its approximately 1/10th volume remains outside the water. Reason (R): The density of ice is approximately 10% less than the density of water.

A. Both A and R are true but R is NOT the correct explanation of A.

B. A is true but R is false.

C. Both A and R are true and R is the correct explanation of A.

D. A is false but R is true.

Answer: Option C

Solution (By JKExamLibrary)

The density of ice is about 900 kg/m³ (0.9 g/cm³), while pure water is 1000 kg/m³ (1.0 g/cm³). According to the principle of floatation, the fraction of volume submerged is the ratio of densities: ρ_ice / ρ_water = 0.9. This means 90% is submerged, leaving exactly 10% (1/10th) exposed above the surface. Reason R explains Assertion A.

This question belongs to: Science Physics

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A force of 12 N gives an object acceleration 4 m/s². Mass of object is

A. 3 kg

B. 48 kg

C. 8 kg

D. 0.33 kg

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Correct Answer: Option A

Explanation:
m = F/a = 12/4 = 3 kg.

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A thermometer reads 25°C. What is the corresponding temperature in Kelvin?

A. 325 K

B. 273 K

C. 298 K

D. 248 K

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Correct Answer: Option C

Explanation:
To convert a temperature from Celsius to Kelvin, the formula is K = °C + 273.15. For most physics problems, we use 273. Therefore, K = 25 + 273 = 298 K. Kelvin is the SI unit of temperature, and it never uses a degree symbol.

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A ball is thrown vertically upward with speed 20 m/s. The maximum height reached (g = 10 m/s²) is

A. 40 m

B. 200 m

C. 10 m

D. 20 m

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Correct Answer: Option D

Explanation:
Using v² = u² - 2gH, at maximum height v = 0. So 0 = 20² - 2×10×H => 400 = 20H => H = 20 m. Alternative formula: H = u²/(2g) = 400/20 = 20 m. Remember to use consistent units. For quick calculation, u²/(2g) is handy.

This question belongs to: Science Physics

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