Most Asked 2-Marks question 11th NEB Physics
_1.jpg)
Mechanics
Physical Quantities
1. Distinguish between precise and accurate measurements.
2. Is dimensionally correct equation necessarily be a correct physical relation? what about dimensionally wrong equation?
3. The energy of a photon is given by E = hf. Find the dimension and unit of Planck's constant ' h ' , where ' f ' is the frequency of radiation.
4. The length of rod is exactly 1 cm. An observer records the reading as 1.0 cm, 1.00 cm, and 1.000 cm, which is the most accurate measurement?
5. The diameter of s steal rod is given as 56.47 +- 0.02 mm. What does it mean?
6. Name any two physical quantities which have the same dimensions. Can a quantity have unit but no dimension? Explain.
7. Determine the dimensional formula for gravitational constant(G).
8. Check the correctness of the formula t = 2𝜋 √llg using dimensional analysis, ' t ' is the time period of simple pendulum, ' l ' is the length of simple pendulum and ' g ' is the acceleration due to gravity.
9. Check the correctness of the formula, PV = RT.
10. The density of gold is 19.3 gm/cc. Express its value in SI unit.
Vectors
1. If A vector. B vector = 0 (A.B=0), what is the value of angle between A vector and B vector?
2. If vector A = 4i - j + 3k and B = 7i + 5j +k, find the angle between the vector A and B.
3. Is a physical quantity having magnitude and direction necessarily a vector quantity? Explain.
4.Can you find a vector quantity that has a magnitude of zero but components that are different from zero? Explain.
5. What is the difference between scalar and vector products of two vectors? Explain.
6. If B is added to A, under what condition does the resultant vector have a magnitude equal to A + B ? Under what conditions is the resultant vector equal to zero?
7. Can the sum of two equal vectors be equal to either of the vectors? Explain.
Kinematics
1. Is it possible to get a body accelerated even if it is moving with a uniform speed? Justify.
2. From a flying aeroplane a body should be dropped in advanced to hit the target, Why ?
3. Two stones P and Q of different masses m and 2m respectively are dropped simultaneously from the top of a tower and reach the ground with different energies. Which one is faster?
4. A ball is dropped gently from the top of a tower and another ball is thrown horizontally at the same time. Which ball will hit the ground first?
5. A swimmer wants to reach to a point just opposite on the other bank of the river. How should he swim and why?
6. A projectile moves in a parabolic path without air resistance. Is there any point at which its acceleration is perpendicular to the velocity ? Explain.
7. Can you have a zero acceleration but non-zero velocity ? Explain with help of a graph.
8. A bomb is to be dropped from a moving helicopter on a target on the ground. Explain how it can hit the target.
9. Give with an example a case where the velocity of an object is zero but it its acceleration is not zero.
10. Can an object have an eastward velocity experiencing a westward acceleration? Give reason.
Laws Of Motion
1. Explain how Newton's first law of motion follows from the second law.
2.Why does a cricketer lower his hand while catching cricket ball?
3. Why it is easier to pull a body than to push it?
4. Can a body be said to be at rest and in motion at the same time?
5. A man drops his briefcase in an elevator but it does not fall to the floor. What can be concluded about the situation?
6. In rain a scooter may slip on the turning of a road. Why?
7. Why is the kinetic friction less than the limiting friction?
8. Why is it difficult to run fast on sand?
9. Why do we slip on a rainy day?
10. State Newton's second law of motion.
Work and Energy
1. Distinguish between conservative and non-conservative forces.
2. A body is moving with constant velocity v along a circular path of radius r. How much work is done by the centripetal force in revolving the body?
3. The moon is accelerating toward the earth. Why isn't it getting closer to us?
4. What are elastic and inelastic collision ? Give examples.
5. A man carrying a bucket of water is walking on a level road with a uniform velocity . Does he do any work on the bucket while carrying it ?
6. If a moving bullet striking a block of wood on a frictionless table embeds inside it, What happens to the KE of the bullet?
Circular Motion
1. Why is it more difficult to move a stone tied with a longer string than a stone tied with a shorten string?
2. Explain the difference between a simple and conical pendulum.
3. Explain the significance of the banking of a curved road.
4. The positively charged nucleus of an atom attracts the electrons in the orbit. Why do electrons not collapse into the nucleus?
5. If there is a net force acting on a particle in uniform circular motion, Why does the particle's speed not change?
6. What is meant by angular velocity?
7. When a bus takes a turn, passengers are thrown away from the centre of the curved path. Why?
Gravitation
1. Distinguish between gravitational potential and gravitational field strength.
2. An astronaut in a space capsule orbiting the earth experiences weightlessness. Why ?
3. At what condition , does a body becomes weightless at the equator?
4. How does the weight of a body vary on going from earth to moon? Would its mass change?
5. The weight of a body is less inside the earth than on the surface. Explain.
6. Explain why the moon has no atmosphere?
7. If the sun some how collapsed to form a black-hole, what effect would this event have on the orbit of the earth?
8. How does ' g ' at a point vary with the distance from the centre of the earth? Where is the highest value of ' g '? Explain
Equilibrium
1. A passengers in a small boat are not allowed to stand, Why?
2. Does the centre of gravity of a solid body always lie within the material of the body? Explain.
3. A man carrying a load on his back leans forward. Why should he do so?
4. A handle or a knob is fixed at the free end of the door. Explain why?
5.During pregnancy, women often develop back pains from leaning backward while walking. Why do they have to walk this way?
6. What is the difference between centre of mass and centre of gravity of a system?
Elasticity
1. What happen in the Young's modulus of elasticity of a material when the load hanging on its is double?
2. Steel bridge are declared unsafe after a few decades of use. Why?
3. What is elastic limit and breaking stress?
4. Differentiate between elasticity and plasticity .
5. Explain why steel is said to be more elastic than rubber.
Periodic Motion
1. What do you understand by a second's pendulum? If it is taken to moon, will it gain or lose time? Why?
2. How does the frequency of vibration of a simple pendulum related with its length ?
Hence, estimate the frequency of a second's pendulum.
3. A pendulum clock is taken to moon, will it gain or lose the time? Why?
4.Why are bell made of metal and not of wood? Explain.
5. A body is moving in a circular path with constant speed. Is this motion a simple harmonic?
Why?
6. If a pendulum clock is taken to the mountain, will it gain or lose time?
Fluid Statics, Surface Tension and Viscosity
Fluid Statics
1. Why is the bottom of a ship made heavy? Explain.
2.In still air, a helium filled balloon rises up to a certain height and then stops rising. Why?
3. Why do cloud seems to be floating in the sky?
4. A cork is floating in water. What is the apparent weight of the cork?
5. Why is it easier to lift a body in a liquid than in air ?
6. Distinguish between density and specific gravity.
Surface Tension
1. Why does hot soup taste better than cold soup?
2. Why is soap solution a better cleaning agent than ordinary water?
3. Explain why liquid drops are spherical in shape?
4. It is observed that the surface of a liquid in a capillary tube dipped in it is either convex or concave. What may be the reason ? Explain.
5. How does the leaves of tree get water from the ground?
6. Antiseptics used in cuts and wounds of human flesh have low surface tension, Why?
7. What will happen if a capillary tube of insufficient height is dipped in water?
8. Why mercury does not wet the glass tube?
9. We use towels to dry our body after taking a shower, Why?
Viscosity
1. Why is a suction effect experienced by a person standing close to the platform at a station when a fast train passes?
2. Small air bubbles rises slowly while big bubbles rise rapidly through the liquid. Why?
3. Airports at high elevations have longer runways for take offs and landings than the airports at sea level, why?
4. State Bernoulli's theorem.
5. Define viscosity. Does it depend on temperature?
6. Machine parts are jamed in cold day. Why?
7. Define coefficient of viscosity and poise.