A ball is thrown vertically upward with an initial velocity of 20 m/s. What is the maximum height reached? (Take g = 10 m/s²)

The correct answer is B: 20 m. Using v² = u² - 2gh, where final velocity v = 0, u = 20 m/s, g = 10 m/s². Therefore, 0 = 400 - 20h, giving h = 20 m.

In the light-dependent reactions, where exactly does the photolysis of water occur?

The correct answer is B: Thylakoid membrane (lumen side). Water photolysis occurs in the thylakoid lumen as part of Photosystem II, releasing O2, H+, and electrons that drive the electron transport chain.

A radioactive element has a half-life of 10 years. What fraction of the original sample remains after 30 years?

The correct answer is C: 1/8. After 30 years = 3 half-lives: N = N₀ × (1/2)³ = N₀/8. The sample reduces by half three times successively.

Which statement about stomata is INCORRECT?

The correct answer is B: Stomata open during night to minimize water loss. Stomata open during the day (when light is available for photosynthesis) and close at night. This reduces water loss during low photosynthetic activity periods.

Which phenomenon causes the sky to appear blue during daytime?

The correct answer is C: Rayleigh scattering. Blue light has shorter wavelength and is scattered more by atmospheric molecules (Rayleigh scattering)

Government Jobs Exam Preparation — SSC, UPSC, Bank, Railway

Choose Govt Exam

UPSC IAS / IPS SSC CGL / CHSL Bank PO / Clerk Railway RRB / NTPC NDA / CDS / AFCAT General Knowledge Quantitative Aptitude Logical Reasoning English Language History & Polity General Science Current Affairs

All Physics Chemistry Biology Botany Zoology Human Body Disease & Health Space & Astronomy

All Easy Medium Hard

Govt Exam — General Science

SSC · UPSC · Bank PO · Railway · NDA — Government Exam MCQ Practice

96 Questions 10 Topics Take Test

Showing 91–96 of 96 questions

Q.91 Medium Physics

Which of the following correctly describes the photoelectric effect?

A Emission of electrons from a metal when exposed to light of sufficient frequency

B Emission of electrons from a metal when exposed to light of any frequency

C Absorption of light energy by electrons in a metal

D The bending of light around obstacles

Correct Answer: A. Emission of electrons from a metal when exposed to light of sufficient frequency

Explanation:

The photoelectric effect occurs when light of frequency greater than or equal to the threshold frequency strikes a metal surface, causing electron emission. It demonstrates the particle nature of light.

Take Test

Q.92 Medium Physics

A moving object has kinetic energy K. If its velocity is doubled, what will be its new kinetic energy?

A 2K

B 4K

C K/2

D K/4

Correct Answer: B. 4K

Explanation:

Kinetic energy KE = (1/2)mv². When velocity is doubled: KE' = (1/2)m(2v)² = (1/2)m(4v²) = 4 × (1/2)mv² = 4K.

Take Test

Q.93 Medium Physics

Which law of thermodynamics explains why heat cannot spontaneously flow from a colder body to a hotter body?

A First Law of Thermodynamics

B Second Law of Thermodynamics

C Third Law of Thermodynamics

D Zeroth Law of Thermodynamics

Correct Answer: B. Second Law of Thermodynamics

Explanation:

The Second Law of Thermodynamics states that entropy of an isolated system increases or remains constant. Heat spontaneously flows from hot to cold, not vice versa, establishing the direction of processes.

Take Test

Q.94 Medium Physics

A ball is thrown vertically upward with initial velocity 20 m/s. What maximum height does it reach? (g = 10 m/s²)

A 10 m

B 20 m

C 30 m

D 40 m

Correct Answer: B. 20 m

Explanation:

At maximum height, v = 0. Using v² = u² - 2gh: 0 = 20² - 2(10)h. 20h = 400. h = 20 m.

Take Test

Q.95 Medium Physics