What is the young's modulus of a material?
A
Stress/Strain
B
Strain/Stress
C
Force × Area
D
Force/Volume
Correct Answer:
A. Stress/Strain
Explanation:
Young's modulus Y = Stress/Strain = (F/A)/(ΔL/L), a measure of material stiffness
A convex lens of focal length 20 cm is used as a magnifying glass. If an object is placed 5 cm from the lens, what is the nature of the image?
A
Real, inverted, diminished
B
Virtual, erect, magnified
C
Real, erect, diminished
D
Virtual, inverted, magnified
Correct Answer:
B. Virtual, erect, magnified
Explanation:
When object is between lens and focus (u < f), a convex lens produces virtual, erect, magnified image
Which quantum number determines the shape of an orbital?
A
Principal quantum number (n)
B
Azimuthal quantum number (l)
C
Magnetic quantum number (m)
D
Spin quantum number (s)
Correct Answer:
B. Azimuthal quantum number (l)
Explanation:
The azimuthal quantum number (l) determines the shape of the orbital (s, p, d, f)
A wire of resistance R is stretched to double its length. What is the new resistance?
Explanation:
Resistance R = ρL/A. When length doubles, L becomes 2L and area becomes A/2 (volume constant). New R = ρ(2L)/(A/2) = 4ρL/A = 4R
Which phenomenon causes the sky to appear blue during daytime?
A
Reflection of light
B
Refraction of light
C
Rayleigh scattering
D
Total internal reflection
Correct Answer:
C. Rayleigh scattering
Explanation:
Blue light has shorter wavelength and is scattered more by atmospheric molecules (Rayleigh scattering)
A charged particle moves in a magnetic field. Under what condition does it move in a straight line?
A
Velocity is parallel to magnetic field
B
Velocity is perpendicular to magnetic field
C
Magnetic field is very strong
D
Particle has positive charge
Correct Answer:
A. Velocity is parallel to magnetic field
Explanation:
Lorentz force F = q(v × B). When v is parallel to B, the cross product is zero, so no force acts
Which of the following is NOT a vector quantity?
A
Displacement
B
Temperature
C
Velocity
D
Acceleration
Correct Answer:
B. Temperature
Explanation:
Temperature is a scalar quantity as it has only magnitude. Displacement, velocity, and acceleration are vector quantities as they have both magnitude and direction.
Which law states that the force of attraction between two masses is directly proportional to the product of their masses and inversely proportional to the square of the distance between them?
A
Newton's First Law
B
Newton's Second Law
C
Newton's Law of Gravitation
D
Kepler's First Law
Correct Answer:
C. Newton's Law of Gravitation
Explanation:
Newton's Law of Universal Gravitation states F = G(m₁m₂)/r². This is the fundamental law describing gravitational attraction between masses.
What is the atomic mass unit (amu) equivalent to in kg?
A
1.66 × 10⁻²⁷ kg
B
1.66 × 10⁻²⁴ kg
C
1.66 × 10⁻³⁰ kg
D
1.66 × 10⁻³³ kg
Correct Answer:
A. 1.66 × 10⁻²⁷ kg
Explanation:
1 amu = 1.66054 × 10⁻²⁷ kg. This is used to express atomic and molecular masses.
A body falls freely from rest. What is its velocity after 2 seconds? (g = 10 m/s²)
A
10 m/s
B
20 m/s
C
30 m/s
D
40 m/s
Correct Answer:
B. 20 m/s
Explanation:
Using v = u + gt, where u = 0 (at rest), t = 2s, g = 10 m/s². Therefore v = 0 + 10 × 2 = 20 m/s.
