CAPF (AC) 2020 (Paper-1) (Question 1-50)

Total Questions: 50

1. Which one of the following statements for an object falling freely under the influence of gravity is correct?

(a) Zero acceleration always implies zero velocity
(b) Zero acceleration has no relation with the velocity of the object
(c) Zero velocity at any instant necessarily means zero acceleration at that instant
(d) Acceleration is constant all throughout the free fall

Correct Answer: (d) Acceleration is constant all throughout the free fall

Solution:A. Acceleration is the rate of change of velocity with respect to time, if the acceleration of an object is zero, then it may be moving with constant velocity. Zero velocity does not mean an object has zero acceleration at that instant. During a free fall, the acceleration is constant throughout the fall.

2. Two magnetic field lines produced by the same source

(a) never intersect
(b) can originate from same point
(c) can terminate at same point
(d) can intersect depending on situation

Correct Answer: (a) never intersect

Solution:It is the property of the magnetic field line produced by the same source that they never intersect each other. Magnetic field lines travel from the North Pole of the magnet towards it the South Pole outside the magnet and from the South Pole to the North Pole inside the magnet. It is true that no two magnetic field lines ever intersect each other.

3. Which one of the following statements regarding Fleming's Rule is correct?

(a) Fleming's left hand rule gives direction of force on a current-carrying conductor in a magnetic field
(b) Fleming's right hand rule gives direction of force on a current-carrying conductor in a magnetic field
(c) Both the left-hand and right-hand rule can be used for finding direction of force on a current-carrying conductor in a magnetic field
(d) Fleming's rule has nothing to do with magnetic field

Correct Answer: (a) Fleming's left hand rule gives direction of force on a current-carrying conductor in a magnetic field

Solution:According to Fleming's Left-Hand Rule, the direction of force/motion of the conductor in a current-carrying conductor can be found in the magnetic field direction and the current direction is known. The force experienced by the conductor is perpendicular to both the field and to the direction of the current flow.

4. Which one of the following statements regarding motion is correct?

(a) All the periodic motions are necessarily simple harmonic
(b) All the simple harmonic motions are necessarily periodic motions
(c) There is no co-relation between the simple harmonic motions and the periodicity of motion
(d) The relation between the simple harmonic motion and periodic motion depends upon the mass of object undergoing the motion

Correct Answer: (b) All the simple harmonic motions are necessarily periodic motions

Solution:C. Simple harmonic motion is a type of periodic motion where the restoring force is directly proportional to the displacement.

5. The radar used by police to check over-speeding vehicles works on the principle of

(a) Raman effect
(b) Induction effect
(c) Doppler effect
(d) Coulomb effect

Correct Answer: (c) Doppler effect

Solution:Doppler Effect is used to measure speed in Radar sensors used by police to detect over-speed vehicles. When the fixed-frequency radio wave sent from the sender continuously strikes an object that is moving towards or away from the sender, the frequency of the reflected radio wave is changed and it is detected.

6. Which one of the following statements with regard to Newton's third law of motion is NOT correct?

(a) Force never occurs singly in nature
(b) When the earth pulls a stone downwards due to gravity, the stone exercise a force on the earth
(c) There is a cause-effect relation implied in the third law
(d) There is no cause-effect relation implied in the third law

Correct Answer: (c) There is a cause-effect relation implied in the third law

Solution:There is no cause-effect relation between action and reaction. According to the third law of motion every acting force has to face an equal and opposite reactive force.

The reaction force is not an effect of the acting force and neither the acting force is a cause of the reactive force. The reactive force comes into action as soon as a force is applied there is simply no cause and effect relationship between action and reaction.

7. Magnesium is used in

(a) fireworks to make a bright white light
(b) gemstones in jewellery
(c) examination of alimentary canal of the patient
(d) purification of water

Correct Answer: (a) fireworks to make a bright white light

Solution:Magnesium is used in fireworks like crackers. It burns a very bright white due to this it is added to give white sparks and overall brilliance of a firework.

8. Which one of the following ingredients does NOT constitute paint?

(a) Turpentine oil (thinner)
(b) Poly-hydroxy phenols (anti-skinning agent)
(c) Thiourea (accelerator)
(d) Titanium dioxide (pigment)

Correct Answer: (c) Thiourea (accelerator)

Solution:Thiourea is not a constituent of paint. All others like pigment, ant skinning agents and thinner are the main components of paint. Thiourea has a wide range of uses; for example, it is used in the production and modification of textile and dyeing auxiliaries, in the leaching of ores, in the production of pharmaceuticals and pesticides, as a vulcanization accelerator, and as an auxiliary agent in the diazo paper.

9. Which one of the following statements about alkaline earth metals is NOT true?

(a) Strontium salts burn with a red flame
(b) Barium metal is used in medicine to examine the alimentary canal of a patient by X-ray
(c) Green plants need magnesium in order to make the chlorophyll that trap the energy from sunlight in photosynthesis
(d) Red colour of gemstone Ruby is due to the element beryllium present in it

Correct Answer: (d) Red colour of gemstone Ruby is due to the element beryllium present in it

Solution:The red colour of ruby is due to the presence of traces of Chromium and not Beryllium. The colour can range from orange-red to red or purplish-red.

10. Which one of the following gases produces a red light when electricity flows through it?

(a) Helium
(b) Argon
(c) Nitrogen
(d) Neon

Correct Answer: (d) Neon

Solution:When electricity is passed through neon gas it gives rise to red colour. It can give rise to a colour ranging from orange to red light. A sealed glass tube with a metal electrode at each end filled with neon gas at low pressure emits orange-red light when the high potential is applied to the electrodes.

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