Q1. A 10 kg object is moving with a speed of 5 m/s. What is its momentum? (2022)
Solution:
Momentum = mass × velocity = 10 kg × 5 m/s = 50 kg m/s.
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Q2. A concave mirror has a focal length of 20 cm. What is the radius of curvature of the mirror? (2021)
Solution:
The radius of curvature (R) is twice the focal length (f). Therefore, R = 2f = 2 * 20 cm = 40 cm.
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Q3. What is the decibel level of a sound that is perceived as the threshold of hearing? (2022)
Solution:
The threshold of hearing is defined as 0 dB.
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Q4. If the frequency of an AC circuit is doubled, what happens to the inductive reactance?
Solution:
Inductive reactance (X_L) is given by X_L = 2πfL. If the frequency (f) is doubled, the inductive reactance also doubles.
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Q5. What is the focal length of a diverging lens if the image distance is -15 cm and the object distance is -10 cm? (2023)
Solution:
Using the lens formula 1/f = 1/v - 1/u, we find f = -20 cm.
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Q6. If the resistance of a conductor is doubled, what happens to the current if the voltage remains constant? (2020)
Solution:
According to Ohm's Law, if the resistance is doubled while the voltage remains constant, the current will be halved.
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Q7. An object is thrown horizontally from a height of 45 m. How long will it take to hit the ground? (Take g = 10 m/s²) (2022)
Solution:
Using h = (1/2)gt², 45 = (1/2)(10)t². Solving gives t² = 9, so t = 3 s.
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Q8. What is the magnetic field strength at the center of a circular loop of radius r carrying a current I?
Solution:
The magnetic field at the center of a circular loop is given by B = (μ0I)/(2r).
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Q9. In which medium does sound travel the slowest?
Solution:
Sound travels slowest in air compared to water and solids like steel.
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Q10. A 1 kg block of metal at 100°C is placed in 2 kg of water at 20°C. If the final temperature is 30°C, what is the specific heat capacity of the metal? (2023)
Solution:
Using conservation of energy: m1c1(T1 - Tf) = m2c2(Tf - T2), we find c1 = 2 J/kg°C.
