Work, Energy and Sound

A ball is thrown vertically upward with a force of 50 N. What is the work done by the gravitational force during the upward motion of the ball?

1. Positive
2. Zero
3. Negative
4. Depends on the mass of the ball

Answer: (c) Negative

A rock is thrown straight up with an initial velocity. At the highest point, which of the following is true about the work done by gravity?

1. Work done is zero
2. Work done is positive
3. Work done is negative
4. Work done is maximum

Answer: (c) Work done is negative

If a sound wave has a wavelength of 2 m and a frequency of 500 Hz, what is its speed?

1. 10 m/s
2. 100 m/s
3. 200 m/s
4. 1000 m/s

Answer: (d) 1000 m/s

The intensity of a sound wave is inversely proportional to the square of the distance from the source. If the distance from the sound source is doubled, what happens to the intensity of the sound?

1. It doubles.
2. It becomes four times stronger.
3. It is halved.
4. It becomes one-quarter as strong.

Answer: (d) It becomes one-quarter as strong.

A box is being dragged across a rough floor with a constant velocity by applying a force of 100 N forward. If the frictional force opposing the motion is also 100 N, what is the work done by friction after moving the box for 5 meters?

1. 500 J
2. -500 J
3. 0 J
4. 100 J

Answer: (b) -500 J

Assertion (A): A ball thrown upward has negative work done by gravity. Reason (R): The force due to gravity acts downward, opposite to the displacement of the ball. Choose the correct option:

1. Both A and R are true, and R is the correct explanation of A
2. Both A and R are true, but R is not the correct explanation of A
3. A is true, but R is false
4. A is false, but R is true

Answer: (a) Both A and R are true, and R is the correct explanation of A

A sound analysis software records the voices of two singers, Singer X and Singer Y, while they sustain a single note. Their wave properties are recorded below: Which singer’s voice would sound louder, and why?

1. Singer X, because the amplitude is larger, indicating higher loudness
2. Singer Y, because the lower amplitude reduces air resistance
3. Both have the same loudness because their wave patterns are identical
4. Singer X, because the frequency is lower, which makes the sound more powerful

Answer: (a) Singer X, because the amplitude is larger, indicating higher loudness

A student plots two sound waves traveling through air and water on the same graph. The wave in water has a shorter wavelength but the same frequency as the wave in air. Which conclusion can be drawn from this graph?

1. Sound travels slower in water than in air
2. The frequency of sound changes when it moves from air to water
3. The speed of sound in water is greater than in air
4. The amplitude of the sound wave changes when moving between media

Answer: (c) The speed of sound in water is greater than in air

A 30 kg object slides down a rough incline of 5 m length at an angle of 60°. If the coefficient of friction is 0.5, what is the work done by friction?

1. -300 J
2. -375 J
3. 375 J
4. 450 J

Answer: (b) -375 J

A tuning fork produces a sound of frequency 512 Hz. The sound travels through two rooms: Room 1 is at 0°C. Room 2 is at 30°C. What happens to the wavelength of the sound wave when it moves from Room 1 to Room 2?

1. It increases because speed of sound increases
2. It decreases because frequency decreases.
3. It remains the same because frequency is constant.
4. It increases because frequency increases.

Answer: (a) It increases because speed of sound increases