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General ScienceMediumAsked in: CDS · CDS-II 2019, GK

A car undergoes a uniform circular motion. The acceleration of the car is

  1. A.zero
  2. B.a non-zero constant
  3. C.a non-zero but not a constant
  4. D.None of the above

Correct answer

C. a non-zero but not a constant

Explanation

The correct answer is C, a non-zero but not a constant. In uniform circular motion the speed stays the same, but the direction of the velocity keeps changing, so the car is always accelerating and the direction of that acceleration keeps changing too.

Acceleration is the rate of change of velocity, and velocity is a vector with both size and direction. On a circular path the velocity at every point is along the tangent, so it turns continuously. The resulting centripetal acceleration has a fixed size, v squared divided by r, but it always points towards the centre of the circle. As the car moves round, this direction rotates, so the acceleration vector is not constant.

A is wrong because zero acceleration would mean motion in a straight line at constant speed. B is wrong because only the size of the acceleration is constant; its direction changes at every instant. D is wrong because option C describes the motion correctly.

Exam tip: uniform circular motion means constant speed, changing velocity, and centripetal acceleration v²/r always directed to the centre.

Practice Questions

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Q1.General ScienceAsked in: UPSC Civil Services · CSE Prelims 2022, GS Paper IMedium

Which of the following are nitrogen-fixing plants?

1. Alfalfa

2. Amaranth

3. Chickpea

4. Clover

5. Purslane (Kulfa)

6. Spinach

Select the correct answer using the code given below:

  1. A.1, 3 and 4 only
  2. B.1, 3, 5 and 6 only
  3. C.2, 4, 5 and 6 only
  4. D.1, 2, 4, 5 and 6
Show answer
Correct answer: A. 1, 3 and 4 only

Alfalfa, chickpea and clover are legumes, and legumes fix nitrogen. Plants of the legume family (Fabaceae) carry root nodules that house Rhizobium bacteria.

Q2.General ScienceAsked in: UPSC CAPF · CAPF 2017, Paper IMedium

The mass number of an element is NOT changed when it emits

  1. A.Alpha and Beta radiations only
  2. B.Alpha and Gamma radiations only
  3. C.Beta and Gamma radiations only
  4. D.Alpha, Beta and Gamma radiations
Show answer
Correct answer: C. Beta and Gamma radiations only

Neither beta nor gamma emission changes the total number of protons and neutrons in a nucleus, so the mass number stays the same.

Q3.General ScienceAsked in: UPSC CAPF · CAPF 2025, Paper IMedium

Which one among the following statements about facilitated transport in plants is correct?

  1. A.All passive transports are types of facilitated transport.
  2. B.Facilitated transport is an example of active transport.
  3. C.Water moves across plasma membrane by active transport.
  4. D.Facilitated transport requires assistance of carrier proteins.
Show answer
Correct answer: D. Facilitated transport requires assistance of carrier proteins.

In facilitated transport, molecules cross the membrane with the help of membrane proteins, while still moving down their concentration gradient.

Q4.General ScienceAsked in: UPSC CAPF · CAPF 2017, Paper IMedium

Who among the following has coined the term 'Quark', the fundamental particles that make up protons and neutrons in an atomic nucleus ?

  1. A.Richard Feynman
  2. B.Murray Gell-Mann
  3. C.Albert Einstein
  4. D.Niels Bohr
Show answer
Correct answer: B. Murray Gell-Mann

The American physicist Murray Gell-Mann proposed quarks in 1964 and gave them their name. Gell-Mann, and independently George Zweig, suggested that protons, neutrons and other such particles are built from smaller units.