A body of mass 5 kg is moving with momentum 20 kg m/s. Its velocity is:
A. 2 m/s
B. 4 m/s
C. 100 m/s
D. 0.25 m/s
Correct Answer: B v = p/m = 20/5 = 4 m/s.
Q2. Biology
Which enzyme breaks down starch in the mouth?
A. Amylase
B. Pepsin
C. Lipase
D. Trypsin
Correct Answer: A Salivary amylase (ptyalin) breaks down starch into maltose in the oral cavity.
Q3. Physics
The de Broglie wavelength of an electron accelerated through a potential difference V is given by:
A. h / sqrt(mV)
B. h / sqrt(2meV)
C. h / sqrt(2mVe)
D. h / sqrt(V/2me)
Correct Answer: B When an electron is accelerated through a potential difference V, it gains kinetic energy KE = eV. The kinetic energy is also given by KE = p^2 / 2m, where p is the momentum and m is the mass of the electron. Therefore, p = sqrt(2mKE) = sqrt(2meV). The de Broglie wavelength is given by = h/p. Substituting the expression for p, we get = h / sqrt(2meV).
Q4. Chemistry
Which of the following reactions will NOT yield an alkyl halide?
A.
B.
C.
D.
Correct Answer: D Reaction A (Lucas test) yields CHCHCl. Reaction B (free radical halogenation) yields CHCH(Cl)CH and CHCHCHCl. Reaction C (hydrohalogenation of propene, Markovnikov's rule) yields CHCH(Br)CH. Reaction D (reaction of carboxylic acid with PCl) yields an acyl chloride (CHCHCOCl), not an alkyl halide.
Q5. Biology
The process of cell division for growth is:
A. Meiosis
B. Mitosis
C. Binary fission
D. Budding
Correct Answer: B Mitosis produces identical daughter cells for growth and repair.
Q6. Physics
The coefficient of performance of a refrigerator is given by:
A. Q/W
B. Q/W
C. W/Q
D. (Q-Q)/W
Correct Answer: B COP = Q/W where Q is heat extracted from cold reservoir and W is work input.
The magnetic field at the center of a current carrying circular loop is:
A. Zero
B. I/2R
C. I/R
D. I/4piR
Correct Answer: B B = I/(2R) at center of circular loop.
Q9. Physics
When light of frequency is incident on a photocathode, the stopping potential is V. When light of frequency is incident on the same photocathode, the stopping potential is V. If V > V, which of the following relations is correct? (h is Planck's constant, e is the charge of an electron)
A. h( - ) = e(V - V)
B. h( - ) = e(V - V)
C. h( + ) = e(V + V)
D. h( / ) = e(V / V)
Correct Answer: A According to Einstein's photoelectric equation, the maximum kinetic energy of emitted photoelectrons (KE_max) is given by:
h = + KE_max
where h is Planck's constant, is the frequency of incident light, and is the work function of the metal.
The stopping potential (V_s) is related to KE_max by: KE_max = eV_s
So, the equation becomes: h = + eV_s
For the first case:
h = + eV (Equation 1)
For the second case:
h = + eV (Equation 2)
Subtract Equation 1 from Equation 2:
(h - h) = ( + eV) - ( + eV)
h( - ) = eV - eV
h( - ) = e(V - V)
Q10. Chemistry
The element with electronic configuration 1s^22s^22p3s^23p belongs to:
A. Group 2
B. Group 18
C. Group 16
D. Group 17
Correct Answer: B Full 3p -> noble gas configuration -> Group 18 (Argon).
Q11. Physics
A particle of mass 'm' is projected with velocity 'v' at an angle '' with the horizontal. The magnitude of the change in momentum of the particle from the time of projection till it reaches the maximum height is:
A. mv cos
B. mv sin
C.
D.
Correct Answer: B At the time of projection, the momentum components are Px = mv cos (horizontal) and Py = mv sin (vertical). At the maximum height, the vertical component of velocity becomes zero, so the vertical component of momentum is zero. The horizontal component of momentum remains mv cos. Change in momentum (P) = Final momentum - Initial momentum. P_x = mv cos - mv cos = 0. P_y = 0 - mv sin = -mv sin. The magnitude of the change in momentum is |P_y| = mv sin.
Q12. Physics
A particle moves in a circle of radius 2 m with speed 4 m/s. Its centripetal acceleration is:
A. 2 m/s^2
B. 8 m/s^2
C. 4 m/s^2
D. 16 m/s^2
Correct Answer: B a_c = v^2/r = 16/2 = 8 m/s^2.
Q13. Physics
The energy equivalent of 1 amu is:
A. 931 eV
B. 931 MeV
C. 931 keV
D. 931 J
Correct Answer: B 1 amu = 931.5 MeV/c^2.
Q14. Biology
In a DNA double helix, the two strands are joined by hydrogen bonds between the nitrogenous bases. Which of the following statements about these bonds is correct?
A. Adenine forms two hydrogen bonds with Guanine.
B. Thymine forms three hydrogen bonds with Cytosine.
C. Adenine forms two hydrogen bonds with Thymine.
D. Guanine forms two hydrogen bonds with Cytosine.
Correct Answer: C In the DNA double helix, specific base pairing rules are followed, known as Chargaff's rules:
- Adenine (A) always pairs with Thymine (T) via two hydrogen bonds.
- Guanine (G) always pairs with Cytosine (C) via three hydrogen bonds.
Let's evaluate the options:
A) Adenine forms two hydrogen bonds with Guanine. (Incorrect, A pairs with T, G pairs with C)
B) Thymine forms three hydrogen bonds with Cytosine. (Incorrect, T pairs with A via two H-bonds, C pairs with G via three H-bonds)
C) Adenine forms two hydrogen bonds with Thymine. (Correct)
D) Guanine forms two hydrogen bonds with Cytosine. (Incorrect, G pairs with C via three H-bonds)
Q15. Chemistry
The number of electrons in Na ion is:
A. 11
B. 10
C. 12
D. 9
Correct Answer: B Na (11 e) -> Na loses 1 e -> 10 electrons.