OAT Physics Principles 3 ā Questions and Answers
Question 1: A 500 kg elevator accelerates upward at 2 m/sĀ². What is the tension in the supporting cable? (g = 10 m/sĀ²)
- 4000 N
- 5000 N
- 6000 N (Correct answer)
- 1000 N
Correct answer: 6000 N
T ā mg = ma ā T = m(g + a) = 500(10 + 2) = 6000 N.
Question 2: Which law states that the total electric flux through a closed surface equals the enclosed charge divided by the permittivity of free space?
- Faraday's Law
- Ampere's Law
- Coulomb's Law
- Gauss's Law (Correct answer)
Correct answer: Gauss's Law
Gauss's Law relates total electric flux through a closed (Gaussian) surface to the enclosed charge: Ī¦ = Q_enc/Īµā.
Question 3: A convex lens has a focal length of 20 cm. An object is placed 30 cm from the lens. Where is the image formed?
- 60 cm on the same side as the object
- 60 cm on the opposite side (Correct answer)
- 12 cm on the opposite side
- 12 cm on the same side
Correct answer: 60 cm on the opposite side
1/v ā 1/u = 1/f ā 1/v = 1/20 + 1/30 = 5/60 ā v = 60 cm on the opposite side (real image).
Question 4: Which property of sound determines its perceived loudness?
- Frequency
- Wavelength
- Amplitude (Correct answer)
- Wave speed
Correct answer: Amplitude
Loudness is determined by amplitude (or intensity); greater amplitude causes greater pressure variation and louder sound.
Question 5: A battery of EMF 12 V and internal resistance 1 Ī© is connected to a 5 Ī© external resistor. What is the terminal voltage?
- 12 V
- 10 V (Correct answer)
- 2 V
- 7 V
Correct answer: 10 V
Current I = 12/(1+5) = 2 A; terminal voltage = EMF ā Ir = 12 ā 2(1) = 10 V.
Question 6: An object with mass 3 kg moving at 4 m/s collides and sticks to a stationary 1 kg object. What is the velocity after collision?
- 1 m/s
- 3 m/s (Correct answer)
- 4 m/s
- 12 m/s
Correct answer: 3 m/s
Conservation of momentum: (3)(4) = (3+1)v ā v = 12/4 = 3 m/s.
Question 7: Which of the following describes the Doppler effect for light when a source moves away from an observer?
- Blueshift ā observed frequency increases
- Redshift ā observed frequency decreases (Correct answer)
- No change in frequency
- Increase in speed of light
Correct answer: Redshift ā observed frequency decreases
When a light source recedes, the wavelength stretches (redshift) and the observed frequency decreases.
OAT Physics Principles 3
A 500 kg elevator accelerates upward at 2 m/sĀ².
What is the tension in the supporting cable? (g = 10 m/sĀ²)