Free Scientific Reasoning MCQs with Answers

61. Why does a guitar produce such a loud sound but when strings detached from the body produce very little sound?

• A. There is a microphone attached near the strings, and a speaker connected to it amplifies the volume
• B. The tension in the strings is exceptionally high, which produces a louder sound
• C. Special kinds of strings are used which enable a louder sound to be produced
• D. Resonance in the soundhole allows for amplification of the sound

Explanation: The correct answer is that the guitar's resonance amplifies the sound. The soundhole and the hollow body of the guitar act as a resonating chamber, amplifying the vibrations from the strings and producing a louder sound. Option A is incorrect because acoustic guitars do not use electronic amplification. Option B is incorrect as string tension primarily affects pitch, not volume. Option C is incorrect because while string type affects tone, the amplification comes from the guitar's structure.

62. Why are soldiers required to break their march before stepping onto any bridge?

• A. To prevent the noise created from marching disturbing the life beneath the bridge
• B. To prevent the bridge collapsing due to resonance
• C. To prevent injury from marching on an incline
• D. To not produce sound which may easily be heard by enemies on the other side

Explanation: At a certain point, the bridge would start oscillating to the same rhythm as that of the marching steps. This oscillation would reach a maximum peak when the bridge can no longer sustain its own strength and hence collapses. Therefore, soldiers are ordered to break their steps while crossing a bridge

63. Which phenomenon is underplay when we tune to different stations on radio?

• A. Resonance
• B. Frequency Modulation
• C. Stationary waves
• D. Refraction

Explanation: When we tune to different stations, we actually change the frequency of carrier wave at which our system will resonate at. Carrier wave is the wave which brings in the information for a given station.

64. How does a microwave primarily work?

• A. It cooks food via conduction
• B. It cooks food via convection
• C. It cooks food via resonance
• D. It cooks food via radiation

Explanation: Microwaves operate by emitting electromagnetic waves that match the natural resonant frequency of water molecules. This causes the molecules to vibrate vigorously, generating heat through molecular friction. This heat cooks the food. Option C is correct because it accurately describes this process of resonance. Option A is incorrect because conduction requires direct contact, which is not how microwaves function. Option B is incorrect as convection involves fluid movement, which is not applicable here. Option D, while partially correct in mentioning radiation, does not highlight the specific mechanism of resonance that is central to microwave cooking.

65. Which of the following produces/is a transverse wave?

• A. Clapping hands horizontally
• B. Clapping hands vertically
• C. Water waves
• D. Pulling and pressing a spring

Explanation: Water waves are transverse waves since the motion of particles is perpendicular to the wave's direction of travel, creating surface ripples. Options A and B involve sound waves, which are longitudinal, meaning the disturbances happen in the same direction as the wave moves. Option D describes the behavior of a spring, which also produces longitudinal waves, characterized by parallel movement of the medium to the wave direction.

66. Why doesnt water leave a bucket despite being upside down when we are swirling it as shown?

• A. The centrifugal force pushes the water away from the center of gravity, countering gravity.
• B. Water has stuck to the bottom of the bucket.
• C. The inertia of the water causes it to move sideways instead of moving in the direction of gravity.
• D. The water has developed a gravitational attraction with the bucket and does not fall.

Explanation: The water remains in the bucket during swirling due to its inertia. As the bucket moves in a circular path, the water tends to continue moving in a straight line due to inertia. However, the bucket provides a barrier that keeps the water moving in a circular path along with it. This motion counters the downward force of gravity, preventing the water from spilling out. Option A is incorrect because centrifugal force does not directly counteract gravity. Option B is incorrect as water does not adhere to surfaces without special conditions. Option D is incorrect due to the negligible impact of gravitational attraction between the water and the bucket compared to inertia.

67. Given below is a food web. Population of which of the following will see a decrease if the number of frogs undergo a drastic decrease?

• A. Birds
• B. Grasshopper
• C. Rabbit
• D. Mouse

Explanation: The number of birds will decrease since snakes can only feed on birds now, so will consume more of them.

68. A student was provided with a slide to view under a microscope. He was not able to spot a nucleus but could see a cell wall, a whip-like structure at one corner of the cell. Which of the following can be the slide that the student was presented?

• A. Red blood cells
• B. Ciliated cells of the trachea
• C. E.coli from the stomach
• D. Fungi mycelium

Explanation: E.coli being a prokaryote lacks nucleus, has a cell wall and may have a flagella

69. An organism has genotype Aa Bb CC Dd. How many different types of combinations are possible for gamete formation?

• A. 2
• B. 4
• C. 8
• D. 16

Explanation: To determine the number of different types of gamete combinations, examine each gene locus: A, B, and D are heterozygous, meaning they each have two alleles that can segregate, while C is homozygous. Thus, the possible combinations are calculated as 2 x 2 x 1 x 2 = 8. Option A underestimates the number of combinations by considering only one variable locus. Option B partly accounts for the variability but misses one heterozygous locus. Option D overestimates by treating all loci as variable, which is incorrect as locus C is not variable. Therefore, the correct answer is Option C, with 8 combinations.

70. If telomerase enzymes are less active than usual, what medical condition will this cause?

• A. Cancer
• B. Premature aging
• C. Cardiovascular disorders
• D. Pneumonia

Explanation: Reduced telomerase activity results in faster telomere shortening, leading to cellular senescence and ultimately contributing to premature aging. This is because telomerase is responsible for maintaining telomere length during cell division. In contrast, cancer is usually associated with increased telomerase activity, allowing cells to divide indefinitely. Cardiovascular disorders may be linked to telomere shortening but are not directly a consequence of decreased telomerase activity. Pneumonia is unrelated to telomerase activity as it is an infectious condition affecting the lungs.