NMMS - National Means-cum-Merit Scholarship Science: Force, Pressure, and Light Questions and Answers — Questions and Answers
Question 1: A student observes that a sharp knife cuts vegetables more effectively than a blunt knife. Which of the following principles best explains this observation?
- The pressure exerted is inversely proportional to the area over which the force is applied. (Correct answer)
- The force applied by a sharp knife is greater than that of a blunt knife.
- The pressure exerted is directly proportional to the area over which the force is applied.
- Friction is greater with a blunt knife, making it harder to cut.
Correct answer: The pressure exerted is inversely proportional to the area over which the force is applied.
Pressure is defined as force per unit area (P = F/A). A sharp knife has a very small surface area at its cutting edge. For the same amount of force applied, this small area concentrates the force, resulting in a very high pressure that is sufficient to cut through the vegetable. A blunt knife has a larger area, so the same force results in lower pressure, which is often insufficient to cut.
Question 2: When a rocket is launched, it pushes hot gases downwards. According to Newton's Third Law of Motion, what is the corresponding reaction force?
- The rocket accelerating upwards. (Correct answer)
- The gravitational force pulling the rocket down.
- The air resistance opposing the rocket's motion.
- The force of the gases pushing against the launchpad.
Correct answer: The rocket accelerating upwards.
Newton's Third Law of Motion states that for every action, there is an equal and opposite reaction. The 'action' is the force of the rocket expelling hot gases downwards. The 'reaction' is the equal and opposite force of the gases pushing the rocket upwards, causing it to accelerate.
Question 3: A beam of white light passes through a glass prism and splits into a spectrum of colors. Which color of light is bent the most?
- Red
- Yellow
- Green
- Violet (Correct answer)
Correct answer: Violet
This phenomenon is called dispersion of light. When white light enters a prism, it refracts. Because the refractive index of glass is slightly different for each color's wavelength, they bend at slightly different angles. Violet light has the shortest wavelength and is slowed down the most, causing it to bend or refract the most. Red light has the longest wavelength and bends the least.
Question 4: Why does a mountaineer climbing at a high altitude often experience nosebleeds?
- The temperature is much lower at high altitudes.
- The atmospheric pressure outside the body is significantly lower than the blood pressure inside. (Correct answer)
- The force of gravity is weaker at high altitudes.
- There is less oxygen available, causing blood vessels to expand.
Correct answer: The atmospheric pressure outside the body is significantly lower than the blood pressure inside.
Atmospheric pressure is the pressure exerted by the weight of the air in the atmosphere. As altitude increases, the amount of air above decreases, so the atmospheric pressure becomes lower. The human body is accustomed to the higher pressure at sea level. At high altitudes, the internal pressure of the blood vessels can be significantly higher than the external atmospheric pressure, which can cause delicate blood vessels, like those in the nose, to rupture.
Question 5: Which of the following is an example of an image formed by a plane mirror?
- A real, inverted, and diminished image.
- A virtual, erect, and magnified image.
- A virtual, erect, and same-sized image. (Correct answer)
- A real, erect, and same-sized image.
Correct answer: A virtual, erect, and same-sized image.
A plane mirror always forms an image that is virtual (cannot be projected onto a screen), erect (upright), and the same size as the object. The image is also laterally inverted (left and right are swapped) and appears to be as far behind the mirror as the object is in front of it.
Question 6: A force of 20 Newtons is applied to an object with a mass of 5 kg. What is the acceleration of the object, assuming no other forces are acting on it?
- 100 m/s²
- 4 m/s² (Correct answer)
- 0.25 m/s²
- 15 m/s²
Correct answer: 4 m/s²
This problem uses Newton's Second Law of Motion, which states that Force = mass × acceleration (F=ma). To find the acceleration, we can rearrange the formula to a = F/m. Given F = 20 N and m = 5 kg, the acceleration is a = 20 N / 5 kg = 4 m/s².
NMMS - National Means-cum-Merit Scholarship Science: Force, Pressure, and Light Questions and Answers
A student observes that a sharp knife cuts vegetables more effectively than a blunt knife.
Which of the following principles best explains this observation?