Class 10 Physics Unit-10: Simple Harmonic Motion and Waves, Solved MCQs With Verified Answers. (National Book Foundation 2022 as Federal Text Book, Islamabad)

1. A mass-spring system has mass m attached to the spring. What will be the effect on the period if its mass is increased four times?

(a) becomes double
(b) becomes half
(c) becomes four times
(d) remains same

... Answer is (a) becomes double
T = 2π `\sqrt frac {m}{k}`

2. A spring is stretched 5 cm by 20 N force, what is its spring constant k?

(a) 100 N/m
(b) 400 N/m
(c) 40 N/m
(d) 4 N/m

... Answer is (b) 400 N/m
F = k x or k =`\frac {F}{x}`

3. If the amplitude of a simple pendulum is doubled, what happens to its time period?

(a) becomes double
(b) becomes half
(c) becomes four times
(d) remains same

... Answer is (d) remains same
T = 2π `\sqrt frac {L}{g}` thus Time period is independent of amplitude

4. Time period of a simple pendulum will be smallest at:

(a) Murree
(b) Moon
(c) Poles
(d) Equator

... Answer is (d) Equator
T = 2π `\sqrt frac {L}{g}` as T is inversely related to square root o g. Hence for a greater value of g, the time period will be smallest. At the equator, the value of g is the greatest.

5. If a body performing simple harmonic motion completes one vibration in 2 seconds, frequency of vibration is:

(a) 2 Hz
(b) 1 Hz
(c) 0.5 Hz
(d) 10 Hz

... Answer is (c) 0.5 Hz
Time period is 2 sec and f = `\frac {1}{T}` = `\frac {1}{2s}` = 0.5 Hz

6. 360 waves are passing through a point in a river in one hour, the time period of the wave is

(a) 0.1 s
(b) 1 s
(c) 10 s
(d) 100 s

... Answer is (c) 10 s
360 wave = 3600 s (1 h) thus time of 1 wave = T = 10 s

7. Time period of the electrical vibrator of the ripple tank is 0.5 s, water waves in the ripple tank have a speed of 10 m/s and an amplitude of 5 cm. The frequency of the waves is: :

(a) 50 Hz
(b) 0.5 Hz
(c) 200 Hz
(d) 2 Hz

... Answer is (d) 2 Hz
f = `\frac {1}{T}` = `\frac {1}{0.5s}` = 2 Hz

8. Which one of the following is a longitudinal wave?

(a) X-rays
(b) Light
(c) String waves
(d) Sound

... Answer is (d) Sound
see the definition of Longitudinal waves from the book

9. . When water waves enter from deep water to shallow water:

(a) frequency of water waves increases
(b) time period of water waves decreases
(c) speed of water waves decreases
(d) wavelength of water waves increases

... Answer is (c) speed of water waves decreases
When water waves enter from deep water region to shallow water region the wavelength decrease, speed decreases, and the frequency remain the same (v = f λ)
 

10. Listening to radio transmission in deep valleys of mountain areas is due to:

(a) reflection of waves
(b) refraction of waves
(c) interference of waves
(d) diffraction of waves

... Answer is (d) diffraction of waves
see the definition of diffraction from the book

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