An object undergoes simple harmonic motion with amplitude 5 cm and frequency 2 Hz. What is the maximum velocity?
A
10π cm/s
B
20π cm/s
C
5π cm/s
D
2.5π cm/s
Correct Answer:
B. 20π cm/s
Explanation:
Maximum velocity in SHM: v_max = ωA = 2πfA = 2π × 2 × 5 = 20π cm/s ≈ 62.8 cm/s.
A submarine sonar uses ultrasound with frequency 50 kHz and speed 1500 m/s in water. What is the wavelength?
A
0.03 m
B
0.3 m
C
3 m
D
30 m
Correct Answer:
A. 0.03 m
Explanation:
Wavelength λ = v/f = 1500/(50 × 10³) = 1500/50000 = 0.03 m = 3 cm. Higher frequencies in denser mediums produce shorter wavelengths.
A conducting sphere is given a charge of 8 μC. What is the electric field at its surface if the radius is 2 cm?
A
1.8 × 10⁶ N/C
B
3.6 × 10⁷ N/C
C
1.8 × 10⁷ N/C
D
7.2 × 10⁷ N/C
Correct Answer:
C. 1.8 × 10⁷ N/C
Explanation:
Electric field at surface: E = kQ/r² = (9 × 10⁹ × 8 × 10⁻⁶)/(0.02)² = (72)/(4 × 10⁻⁴) = 1.8 × 10⁷ N/C.
Two identical objects moving with velocities v and 2v collide and stick together. What fraction of kinetic energy is lost?
Explanation:
Initial KE = ½m(v)² + ½m(2v)² = 2.5mv². Final velocity = 3v/2 (by momentum conservation). Final KE = ½(2m)(3v/2)² = 2.25mv²/4 = 0.84mv². Loss = 2.5 - 0.84 = 1.66, which is 2/3 of initial KE.
A block slides down a frictionless incline of angle 30°. What is its acceleration down the incline?
A
5 m/s²
B
8.66 m/s²
C
9.8 m/s²
D
10 m/s²
Correct Answer:
A. 5 m/s²
Explanation:
On a frictionless incline, a = g sin(θ) = 10 × sin(30°) = 10 × 0.5 = 5 m/s².
A spring with spring constant k = 100 N/m is compressed by 0.1 m. What is the elastic potential energy stored?
A
0.5 J
B
1 J
C
5 J
D
10 J
Explanation:
Elastic PE = ½kx² = ½ × 100 × (0.1)² = ½ × 100 × 0.01 = 0.5 J.
Which phenomenon occurs when sound waves bend around obstacles?
A
Reflection
B
Refraction
C
Diffraction
D
Interference
Correct Answer:
C. Diffraction
Explanation:
Diffraction is the bending of waves around obstacles or through openings. This explains why we can hear sounds around corners.
A light ray travels from air (n=1) into glass (n=1.5) at an incident angle of 30°. What is the refraction angle?
A
15°
B
19.47°
C
22.08°
D
30°
Correct Answer:
B. 19.47°
Explanation:
Using Snell's Law: n₁sinθ₁ = n₂sinθ₂. 1 × sin(30°) = 1.5 × sinθ₂. 0.5 = 1.5sinθ₂. sinθ₂ = 0.333. θ₂ ≈ 19.47°.
Two resistors of 4Ω and 6Ω are connected in series with a 10V battery. What is the total current?
A
1 A
B
2 A
C
10/6 A
D
10/4 A
Explanation:
Total resistance = 4 + 6 = 10Ω. Using Ohm's law: I = V/R = 10/10 = 1 A.
Which of the following is a non-ohmic conductor?
A
Copper wire at constant temperature
B
Tungsten filament in a light bulb
C
Nichrome wire at constant temperature
D
Silver wire at constant temperature
Correct Answer:
B. Tungsten filament in a light bulb
Explanation:
A tungsten filament's resistance changes significantly with temperature during operation, making it non-ohmic. Metals at constant temperature follow Ohm's law.
