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All questions of January Week 4 for NEET Exam

Find the amplitude of the S.H.M whose displacement y in cm is given by equation y= 3sin 157t +4cos157t where t is time in seconds.
  • a)
    20Hz
  • b)
    25Hz
  • c)
    50Hz
  • d)
    40Hz
Correct answer is option 'B'. Can you explain this answer?

When the displacement of a SHM is:
y=a sin wt+ b cos wt
  • Amplitude of the SHM will be:
    A=√a2+b2
Here, a = 3, b = 4
Amplitude, A= √(32+42) = 5 cm
Hence option B is correct.

A second pendulum is mounted in a space shuttle. Its period of oscillations will decrease when rocket is
  • a)
    moving in geostationary orbit
  • b)
    ascending up with uniform acceleration
  • c)
    descending down with uniform acceleration
  • d)
    moving up with uniform velocity
Correct answer is option 'B'. Can you explain this answer?

Top Rankers answered
 
  • Time Period, T = 2π √(l/g')where,
    l = Length of seconds pendulum 
    g’ = Apparent Gravity
  • For the period of oscillations of Seconds Pendulum to decrease, the Apparent gravity (g’) has to increase because:
  • Hence, Time Period of oscillations of Seconds Pendulum will decrease when the rocket is ascending up with uniform acceleration.

 Ethene and ethyne can be distinguished by:
  • a)
    Bromine water
  • b)
    KMnO4 solution
  • c)
    Ammoniacal Cuprous chloride solution
  • d)
    Any of the above
Correct answer is option 'C'. Can you explain this answer?

Nandini Patel answered
The two hydrocarbons can be easily distinguished by simple chemical tests, as ethyne molecule is supposed to have acidic hydrogen.
1. When ethyne is bubbled through ammoniacal silver nitrate solution , a yellow-white precipitate of silver acetylide would be formed.
     C2H2 + 2AgNO3 = Ag2C2 + 2HNO3
2. Similarly, ethyne forms a red precipitate of copper acetylide (Cu2C2) when it is passed through ammoniacal cuprous chloride solution.
Ethene does not react with AgNO3 or Cu2Cl2 solution.

 Propene on ozonolysis forms:
  • a)
    Acetaldehyde
  • b)
    Formaldehyde
  • c)
    Both acetaldehyde and formaldehyde
  • d)
    Acetone
Correct answer is option 'C'. Can you explain this answer?

Raghav Bansal answered
When propene on ozonolysis it yields a new structure called ozonide 
and there cleavage takes place and it yields two products namely 
1.acetaldehyde
2.formaldehyde

If a simple pendulum oscillates with an amplitude 50 mm and time period 2s, then its maximum velocity is
a)0.15 m/s
b)0.1 m/s
c)0.16 m/s
d)0.8 m/s
Correct answer is option 'A'. Can you explain this answer?

Neha Joshi answered
We know that in a simple harmonic motion the maximum velocity,
Vmax = A⍵
Here A = 50 mm
And ⍵ = 2π / T
= 2π / 2
= π
Hence  Vmax = 50 x 10-3
= 0.15 m/s

What will be the phase difference between bigger pendulum (with time period 5T/4 )and smaller pendulum (with time period T) after one oscillation of bigger pendulum?
  • a)
    π/4
  • b)
    π/2
  • c)
    π/3
  • d)
    π
Correct answer is option 'B'. Can you explain this answer?

Preeti Iyer answered
By the time bigger pendulum completes one vibration, the smaller pendulum would have completed 5/4 vibrations. That is smaller pendulum will be ahead by 1/4 vibration in phase. 1/4 vibration means λ/4 path or π/2 radians.

A frequency of 1Hz corresponds to:
  • a)
    2 vibrations per second
  • b)
    1 vibration per second
  • c)
    10 vibrations per second
  • d)
    a time period of ½ second
Correct answer is option 'B'. Can you explain this answer?

Alok Mehta answered
Frequency used to be measured in cycles per second, but now we use the unit of frequency - the Hertz (abbreviated Hz). One Hertz (1Hz) is equal to one vibration per second. So the weight above is bouncing with a frequency of about 1Hz. The sound wave corresponding to Middle C on a piano is around 256Hz.

Ethylene reacts with HBr to give:
  • a)
    Acetylene
  • b)
    Ethyl alcohol
  • c)
    Acetaldehyde
  • d)
    Ethyl bromide
Correct answer is option 'D'. Can you explain this answer?

Preeti Iyer answered
Ethylene reacts with HBr to form Ethyl bromide. The reaction propagates as follow:-
H2C=CH2  +  HBr → H2C+-CH3 →H2BrC-CH3 
Since π cloud is electron rich, so HBr dissociates into H+ and Br-. H+ attacks on alkene to give a carbocation and then Br- attacks to get ethyl bromide.

 Cis isomer have:
  • a)
    High boiling point than trans isomer
  • b)
    Lower boiling point than trans isomer
  • c)
    Same boiling point
  • d)
    None of the above
Correct answer is option 'A'. Can you explain this answer?

Rajat Kapoor answered
The cis isomer in this case has a boiling point of 60.3 degC, while the trans isomer has a boiling point of 47.5 degC. In the cis isomer the two polar C-Cl bond dipole moments combine to give an overall molecular dipole, so that there are intermolecular dipole–dipole forces (or Keesom forces), which add to the London.

 When H+ attacks CH3 – CH = CH2 , carbonation which is more stable is
  • a)
    CH3 – CH2 – CH2
  • b)
    CH2+ – CH2 – CH3
  • c)
    CH3 – CH+ – CH2
  • d)
    CH3 – CH2 – CH2+
Correct answer is option 'C'. Can you explain this answer?

Nitin Khanna answered
CH3 – CH = CH2 → CH3 – CH+ – CH2
The reason for this is only that carbocation is formed which has maximum stability. In this case, we have 6 α-H while for option a, b and d; we have 0, 2 and 2 α-H respectively. So only carbocation in option c forms.

The membrane which cover the brain and the spinal cord is :-
  • a)
    White matter
  • b)
    Grey matter
  • c)
    Peritonium
  • d)
    Meninges
Correct answer is option 'D'. Can you explain this answer?

Meninges are the membranes that cover and protect the brain and spinal cord. There are three layers of meanings: dura mater (closest to the bone), arachnoid (loosely around the brain), pia mater (closely attached to the brain and spinal cord surface).

Which of the following is a richly vascular layer with lots of blood capillaries :-
  • a)
    Duramater
  • b)
    Piamater
  • c)
    Epidermis of skin
  • d)
    Both (1) & (2)
Correct answer is option 'B'. Can you explain this answer?

Riya Banerjee answered
The pia mater of the brain is the innermost of the three membranes, that cover it. It is the vascular membrane of the brain. It carries the minute branches of the two internal carotids and the two vertebral arteries. It also returns the blood to the heart. The dura mater is the most external membrane of the brain. It forms the internal periosteum of the skull. The dura mater is a dense, tough, inelastic fibrous membrane. The epidermis contains no blood vessels, and cells in the deepest layers are nourished by diffusion from blood capillaries extending to the upper layers of the dermis. So, the correct answer is option B.

Corpus callosum connects :-
  • a)
    Two cerebral hemisphere
  • b)
    Two optic lobes
  • c)
    Two olfactory lobes
  • d)
    Optic chiasma
Correct answer is option 'A'. Can you explain this answer?

Anjali Iyer answered
The part of the brain that connects the two hemispheres of the brain is called the corpus callosum. It contains a bundle of neuronal fibers found in humans and other higher order mammals that allow the two hemispheres to talk to one another.

Where is the midbrain located?
  • a)
    Between hypothalamus and pons
  • b)
    Between cerebrum and hypothalamus
  • c)
    Between cerebellum and medulla
  • d)
    Between pons and medulla
Correct answer is option 'A'. Can you explain this answer?

Top Rankers answered
The midbrain is located between the hypothalamus of the forebrain and the pons of the hindbrain. The midbrain is also known as the mesencephalon and controls several motor movements.

A particle of mass 10 gm lies in a potential field v = (50x2+100) J/kg. The value of frequency of oscillations in cycle/sec is
  • a)
    5/π
  • b)
    50/π
  • c)
    10/π
  • d)
    100/π
Correct answer is option 'A'. Can you explain this answer?

Correct option: A
Mass is m = 10 g = 0.01 kg.
The actual potential energy is U = m × (potential per unit mass); the quadratic contribution is Uq = 50 m x2.
Compare with U = (1/2) k x2. Thus (1/2) k = 50 m, so k = 100 m.
Angular frequency satisfies ω² = k/m. Substituting gives ω² = 100, hence ω = 10 rad s-1.
Frequency is f = ω / (2π) = 10 / (2π) = 5/π Hz. Therefore option A is correct.

Which part of the neuron is present in a high concentration in the grey matter?
  • a)
    Cell body
  • b)
    Axon
  • c)
    Dendrites
  • d)
    Synaptic knobs
Correct answer is option 'A'. Can you explain this answer?

Gayatri Desai answered
Grey Matter and Neurons

Grey matter is a type of neural tissue found in the brain and spinal cord. It consists of cell bodies, dendrites, and synapses, and appears grey due to the presence of unmyelinated axons and glial cells. Neurons are the functional units of the nervous system and they transmit information through electrical impulses.

Concentration of Cell Bodies in Grey Matter

The grey matter contains a high concentration of cell bodies compared to other parts of the neuron. The cell body, also known as the soma or perikaryon, is the main part of the neuron that contains the nucleus and various organelles necessary for cellular functions. It is responsible for maintaining the metabolic and structural integrity of the neuron.

Functions of Cell Bodies

The cell body plays several important roles in the neuron:

1. Protein synthesis: The cell body contains ribosomes and other organelles involved in protein synthesis. It produces proteins that are essential for the survival and functioning of the neuron.

2. Metabolism: The cell body generates energy and metabolizes various substances required for neuronal processes. It produces ATP through cellular respiration to fuel the neuron's activities.

3. Integration of information: The cell body receives signals from dendrites and processes them. It integrates these signals and determines whether to transmit or inhibit the electrical impulse.

4. Structural support: The cell body provides structural support to the neuron by giving it its shape and stability. It also connects to other neurons through synapses.

Conclusion

In conclusion, the cell body is present in a high concentration in the grey matter. It is responsible for various vital functions such as protein synthesis, metabolism, integration of information, and structural support. Understanding the distribution and functions of different parts of the neuron, including the cell body, is essential in comprehending the complexity of the nervous system and its role in various physiological processes.

The box like bony structure which encloses the brain is called :-
  • a)
    Cranium
  • b)
    Pericardium
  • c)
    Peritoneum
  • d)
    Periosteum
Correct answer is option 'A'. Can you explain this answer?

Ramesh Chand answered
The box enclosing and protecting the brain is called as the cranium . The cranium is the part of the skull, that encloses the brain. Therefore option A is the correct answer.

Cerebellum is concerned with :-
  • a)
    Co-ordination of muscular movement
  • b)
    Memory
  • c)
    Vision
  • d)
    Reflex action
Correct answer is option 'A'. Can you explain this answer?

Sanjana Singh answered
Cerebellum is a part of the brain and is responsible for motor control which includes muscle movement , equilibrium and balance as it relates to movement .
So 'a' is correct.

The periodic time (tp) is given by
  • a)
    ω / 2 π
  • b)
    2 π / ω
  • c)
    2 π × ω
  • d)
    π/ω
Correct answer is option 'B'. Can you explain this answer?

Divyansh Saha answered
Periodic time is the time taken for one complete revolution of the particle.
∴ Periodic time, tp = 2 π/ω seconds.

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