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

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.

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.

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.

Fleming’s right-hand rule is employed in generators. Fleming’s right-hand rule is used when a conductor travels in a magnetic field region to identify the route of induced current in the conductor. When a conductor coupled to a circuit travels in a magnetic field, the rule displays the path of the induced current.

When a closed circuit exists, the Fleming right-hand rule can determine the direction of current in a generator’s windings. Faraday’s law of induction causes the EMF to be induced in the coil. The direction of current flow in the generator winding can also be determined using the Fleming right-hand rule.

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

Oscillation Motion:- To and fro motion of a particle about a mean position is called an oscillatory motion in which a particle moves on either side of equilibrium (or) mean position is an oscillatory motion.
Examples:- Oscillation of Simple Pendulum, Spring-Mass System.
In an oscillatory motion, the net force on the particle is zero at the mean position.

Periodic Motion:- A motion repeats itself after an equal interval of time.
Examples:- uniform circular motion.
There is no equilibrium position, no restoring force, no stable equilibrium position.

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.

Raman effect: Inelastic scattering of light by molecules, changing the frequency of the light (spectroscopy).
Induction effect: Electronic effect in organic chemistry due to the polarization of o bonds.
Coulomb effect: Electrostatic force of attraction or repulsion between charged particles (Coulomb's Law).

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.

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.

• Magnesium is prized for its ability to burn at extremely high temperatures—around 5,610°F (3,100°C)—producing a pure, white-hot glow that no other element can match.
• When magnesium ignites, it burns rapidly and brightly, filling the sky with intense white sparks.
• This makes it perfect for adding contrast and clarity to firework displays, especially during grand finales and high-altitude bursts.
• It also enhances the vibrancy of coloured effects by acting as a white-light amplifier, making reds redder, blues bolder, and greens more vivid.
• Whether it’s in professional-grade aerial shells or compact cakes and rockets, magnesium ensures that your display isn’t just seen—it’s remembered.
• From huge events to backyard celebrations, magnesium brings the brilliance that turns good fireworks into spectacular ones.

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.

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.

The alkaline earth metals are the elements that correspond to group 2 of the modern periodic table. This group of elements includes beryllium, magnesium, calcium, strontium, barium, and radium.

The elements of this group are quite similar in their physical and chemical properties. For example, all alkaline earth metals are silvery-white-coloured solids under standard conditions. They are also highly lustrous (shiny) and are quite reactive.

The general electronic configuration of these elements is N1S2. Since the alkaline earth metals have a completely full s-orbital in their respective valence shells, they tend to readily lose two electrons to form cations with a charge of +2. Thus, the most common oxidation state exhibited by alkaline earth metals is +2.

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.