Regards,
Tony
“if you set up a pendulum aboard an orbiting space vehicle, would the period be less than, the same as, or greater than it would be in our lab? explain.”Ans:
If you set a pendulum atop Mt. Everest, would the period be less than, greater than or equal to the period you would get in the lab? Explain.Ans:
“The planets are moving around the sun and the gravitational force is used in providing the necessary centripetal force (The force required by a body to move in a circular path). As long as the planets are in motion, they will not move towards the sun. A similar explanation hold good for moon going around earth also.”
1. Is there possibility to transport people upstairs by mechanism of Archimedes' screw?
2. Is there possibility to transmutate Carbon Dioxide to Helium? At what energy expand it is possible if any?
Asked Jacez
Do you know the answer have any comments please respond
Hale asked:
One side of the roof of a building slopes up at 33.5°. A roofer kicks a round, flat rock that has been thrown onto the roof by a neighborhood child. The rock slides straight up the incline with an initial speed of 15.0 m/s. The coefficient of kinetic friction between the rock and the roof is 0.430. The rock slides 10.0 m up the roof to its peak. It crosses the ridge and goes into free fall, following a parabolic trajectory above the far side of the roof, with negligible air resistance. Determine the maximum height the rock reaches above the point where it was kicked.
(The question is left for visitors to answer.)
Sumit Asks:
Sir,
While seeing a rickshaw puller struggling to pull heavy weight,I wondered if the load carried by him can be reduced for carrying same weight people.Since the load carried by him is dependent on the horizontal component of frictional force (i.e,µ.mgsinØ) ,cant we apply a spring in the rickshaw so that the effective weight will decrease and hence the load carried by him?
Susmita asked:
Ans:
The word current means flow.
Electric Current refers to charges in motion. The most common way of producing current is by applying a potential difference across the terminals of a conductor. Then the free electrons in the conductor drifts towards the positive terminal.
The current in the circuit can be kept continuous by providing a constant potential difference between two points of the circuit. This is usually done by connecting the ends of the circuit to the terminals of an electrochemical cell (which converts chemical energy to electrical energy) or a dynamo (which converts mechanical energy to electrical energy)
Please refer the following links for more information
Zeenath PV asked:
why earth moves in an elliptical orbit instead of circular one?
Ans:
Please note that ELLIPSE is the more general form for an orbit and CIRCLE is a speacial case of ellipse.
So, it is more general way of saying that the orbits are elliptical. If it were circular, we would have more trouble explaining why they are perfect circles.
The situation where the Sun, for instance, would be exactly in the center of a perfectly circular planetary orbit couldn't happen in our Solar System since there are other planets that would gravitationally affect the orbit and cause it to be immediately non-circular by pulling the object to one side or the other. Any other stable orbit type than a perfectly circular one turns out to be an elliptical orbit.
Read more at : http://www.astro-tom.com/technical_data/why_elliptical.htm
How can you prove that dS in φ =E.dS is dS Cos θ if the area is tilted at an angle ? I need the mathematical Steps.
Ajesh Asked:
Respected sir, in the famous theory of Albert Einstein which is of mass energy equivalence he stated a formula E = mc2 .
sir does this mean that mass can be converted in to energy or the opposite will happen .
it is even stated in the big bang theory that the universe was created with respect to the above theory is that so?
Answer:
The mass energy conversion and the equivalence is a widely discussed topic in relation to the creation of the universe or the Big Bang.
There is some energy missing in calculation when we consider the equivalence; this is called dark energy.
Please read the following links for more details.
http://csep10.phys.utk.edu/astr162/lect/cosmology/hotbb.html
A constant introduced by Einstein (1917) into the equations of general relativity to allow a steady state cosmological solution to the Einstein field equations. The constant was introduced before the concept of the Big Bang had been conceived, so an expanding or contracting universe was regarded as physically implausible, leading Einstein to add as a "fudge factor." In theory, the constant can be derived from quantum field theory, but the derivation has not yet been performed. Einstein's cosmological constant is equivalent to a vacuum energy density, which means it can be put on the left hand side of Einstein's equations with the geometry (as Einstein did), or on the right hand side with the stress-energy, both forms being mathematically equivalent.
The value of in our present universe is not known, and may be zero, although there is some evidence for a nonzero value; a precise determination of this number will be one of the primary goals of observational cosmology in the near future.
The value of the cosmological constant is an empirical issue which will ultimately be settled by observation; meanwhile, physicists would like to develop an understanding of why the energy density of the vacuum has this value, whether it is zero or not. There are many effects which contribute to the total vacuum energy,
including the potential energy of scalar fields and the energy in “vacuum fluctuations” as predicted by quantum mechanics, as well as any fundamental cosmological constant.
If the recent observational suggestions of a nonzero are confirmed, we will be faced with the additional task of inventing a theory which sets the vacuum energy to a very small value without setting it precisely to zero. In this case we may distinguish between a “true” vacuum which would be the state of lowest possible energy which simply happens to be nonzero, and a “false” vacuum, which would be a metastable state different from the actual state of lowest energy (which might well have = 0). Such a state could eventually decay into the true vacuum, although its lifetime could be much larger than the current age of the universe. A
final possibility is that the vacuum energy is changing with time — a dynamical cosmological “constant”. This alternative, which is sometimes called “quintessence”, would also be compatible with a true vacuum energy which was ultimately zero, although it appears to require a certain amount of fine-tuning to make it work.
No matter which of these possibilities, if any, is true, the ramifications of an accelerating universe for fundamental physics would be truly profound.
Read More at
(The question was reformatted to suit the language)Answer: I must congratulate you first for thinking deep and differently. The relativistic increase in mass is given by the equation The increase in mass increases the gravity, but the force of gravity is governed by the value of the universal constant of gravitaton, which is very low (6.67 x 10-11). For the second part of your question, the increase in mass can be calculated to be about 7 times from the equation mentioned above. (Please post your further doubts on this topic as comment to this post so that all related ideas come together.)
Impact parameter is the perpendicular distance between the velocity vectors of two objects (considered to take part in a collision) when they are at infinite distance (at such a distance that there is no interaction between the two particles)
In Rutherford’s alpha scattering experiment, the gold nucleus is at rest and therefore, in this case
Impact parameter is the perpendicular distance between the gold nucleus and the the direction of the velocity vector of alpha particle when the alpha particle is at infinite distance (i.e; the force of interaction between the gold nucleus and the alpha particle is negligibly small)
Ac changes its direction frequently and therefore the ordinary ammeter which is just a galvanometer with a shunt, tends to respond to the magnitude and direction of the instantaneous values of current and in effect it will not show any deflection.
Ac is measured using hot wire ammeter, which is based on the heating effect of current
Galvin Pinto asked;
- List the devices where permanent magnets & electromagnets are used.
- Sketch the pattern of the field lines around a current carrying:
Straight Conductor
Loop of wire
Solenoid
Ans:
Straight Conductor
Loop of wire
Solenoid
Gavin Pinto asked
“A current carrying wire is placed above a magnetic needle. What do you observe? If you want to increase this effect, what will you do? If you want to reverse the effect, what will you do?”
Ans: When a current carrying conductor is placed above a magnetic needle, the magnetic needle is deflected and tends to align itself perpendicular to the conductor. The effect can be increased by increasing the strength of current through the wire or by decreasing the distance.
However, the maximum deflection which can be produced is 90 degree, when the magnetic field produced by the current carrying wire is very much greater than the earth’s magnetic field.
Nagendra chowdary asked : -
“A circular ring of radius r made of a non conducting material is placed with its axis is parallel to a uniform electric field if the ring rotated by 180 degrees Does the flux changes? A Q charge is uniformly distributed on a thin spherical shell If a point charge is brought near it what is the field at the center?Is u r answer depends on whether it is conducting or non conducting?”
“we know that temperature has a properties to make some thing bigger in volume.we say that gas has no particular volume or shape.where we place a gas it takes the shape of that container.my question is- a gas of mass 'm' has a particular number of atoms or molecules.if the gas is not getting any temperature then how it is occupying all the volume of a bigger container.i mean how the inner space of two atoms or two molecules of that particular gas is increasing when i am transferring it to a bigger container.(say,every condition is constant.nothing is changed.)please answer me.”
“can you give me some name of sites where i can get explanations on hydrostatics or the topics of physics.i am now in class 11.”The visitors are requested to respond
"when a wave enters from air to water, its wavelength changes but frequency remains unchanged. why"Answer Velocity of a wave = frequency x time period V = ν λ When a wave travels from one medium to another, its velocity changes and so also is its wavelength, but frequency; which is the number of vibrations produced per second is independent of the medium, remains constant. However, their is a phenomenon called Doppler Effect where the apparent frequency (observed frequency) is different from actual frequency and is caused by the relative movement between the source and observer (listener) Got a better answer? Please post it as comment.
Physical Quantity is a quantity which can be measured. eg; length, mass, force, time etc(The quantities which cannot be measured are abstract. Eg; Love, anger intelligence)
“we know that temperature has a properties to make some thing bigger in volume.we say that gas has no particular volume or shape.where we place a gas it takes the shape of that container.my question is- a gas of mass 'm' has a particular number of atoms or molecules.if the gas is not getting any temperature then how it is occupying all the volume of a bigger container.i mean how the inner space of two atoms or two molecules of that particular gas is increasing when i am transferring it to a bigger container.(say,every condition is constant.nothing is changed.)please answer me.â€
can you give me some name of sites where i can get explanations on hydrostatics or the topics of physics.i am now in class 11Master will be answering the question shortly. The visitors are requested to respond
"A stone is thrown in a vertically upward direction with a velocity of 5m/s. If the acceleration of the stone during its motion is 10m/s^2 in the downward direction , what will be the height attained by the stone and how much time will it take to reach there?"Answer: Take, u=5m/s a= -10 m/s2 v=0 at the topmost position S= Hmax = ? The eqn of motion to use v2 - u2 = 2aS Which gives H = 1.25 m From the eqn v=u + at t= 0.5 s
"The differential equation and solution for finding the time of death of a patient"
Answer:
See that the question is to find the time of death (Not predicting the time of death. I thought that when I read it first.)
I can give some links which will be helpful in this connection
"Two wires A and B of equal lengths,different cross-sectional areas and made of same metal a)name the property which is same for both the wires. b)name the property which is different for both the wires"Answer:
Since both the wires are of same metal, the resistivity will be same for both whereas since the dimensions (Area of cross section here) are different, the resistance will be different
"What is meant by potential difference?"Answer:
"Potential Difference between two points is the difference in Potential between the two points and is equal to the work done per unit charge ion carrying a positive test charge from one point to another against the electric field and without any acceleration"
"What are the limitations of homogenity?"The question is acutually"What are the limitations of dimensional analysis?" The dimensional analysis is based on the principle of homogenity of dimensions. The question is already discussed earlier HERE
"Why is geothermal energy an alternative source of nuclear energy?"There is some problem with the doubt you asked. It is correct to say "Geothermal energy and Nuclear energy are alternative sources of energy" Sun is the ultimate source of energy for earth. The energy of fuels, wind energy, water energy, food - all these are derived from sun. But Geothermal energy and nuclear energy are not derived from solar energy. GeoThermal Energy Links for Reference http://www.renewableenergyworld.com/rea/tech/geothermal-energy http://www.geos.iitb.ac.in/geothermalindia/pubs/geoweb.htm See a diagram of Geothermal plant [caption id="" align="alignleft" width="525" caption="Geo Thermal Energy"][/caption] The centre of the Earth is around 6000 degrees Celsius - easily hot enough to melt rock. Even a few kilometres down, the temperature can be over 250 degrees Celsius if the Earth's crust is thin. In general, the temperature rises one degree Celsius for every 30 - 50 metres you go down, but this does vary depending on location In volcanic areas, molten rock can be very close to the surface. Sometimes we can use that heat. Geothermal energy has been used for thousands of years in some countries for cooking and heating. The name "geothermal" comes from two Greek words: "geo" means "Earth" and "thermal" means "heat". Read More on Geothermal Energy Here
Indian Institute of Science (IISc), Bangalore is all set to launch a new four-year undergraduate (UG) Bachelor of Science (BS) programme in the coming academic session in 2011. The main aim of the course is to prepare young minds for research and doctoral studies in the upcoming areas of science and technology. Besides motivating students to take up higher research, mentoring and tutorials, the programme will introduce rigorous specializations in fourth, fifth, and sixth semesters. The students will be allowed to choose electives from other streams as well during this period. In the seventh and eighth semesters, students will work on a research-oriented project supervised by a faculty member. Admissions to the programme will be based on national entrance examinations like IIT JEE, AIEEE, AIPMT, and Kishore Vaigyanik Protsahan Yojana.
HALF YEARLY EXAMINATION SAMPLE PAPER
(QUESTIONS ARE FROM THE PART 1 NCERT TEXT BOOK)
CLASS: XI SUB: PHYSICS MM: 70 TIME: 3hrs.
BLUE PRJNT
Sl.No | Unit | VSA(1) | SA I (2) | SA II(3) | LA (5) | Total |
1 | Physical World& Measurement | 2(2) | 4(2) | 3(1) | ------------- | 9(5) |
2 | Kinematics | 1(1) | 4(2) | 6(2) | 5(1) | 16(6) |
3 | Laws of Motion | 1(1) | 2(1) | 6(2) | ----------- | 9(4) |
4 | Work,Energy and Power | 1(1) | 4(2) | 3(1) | 5(1) | 13(5) |
5 | Motion of System of Particles&Rigid Body | 2(2) | 4(2) | 3(1) | 5(1) | 14(6) |
6 | Gravitation | 1(1) | 2(1) | 6(2) | ---------------- | 9(4) |
Total | 8(8) | 20(10) | 27(9) | 15(3) | 70(30) |
General instructions:
(i) All questions are compulsory.
(ii) There are 30 questions in total. Questions 1 to 8 carry one mark each, questions 9to18carry two marks each, questions 19to27carry three marks each and questions 28to30 carry five marks each.
(iii) There is no overall choice. However, an internal choice has been provided in one question of two marks, in one question of three marks and all three questions of five marks each. You have to attempt only one of the given choice in such questions
1. Name the fundamental force which is responsible for the stability of the nucleus. (1)
2. State the no. of significant figures in the following
a) 3.56 x 10-34 b) 0.00005302 (1)
3. A pebble of mass 0.05kg is thrown vertically upwards. Given the direction and magnitude of the net force on the pebble,
(a) During its upward motion
(b) During its downward motion (1)
4. A body is initially at rest. It undergoes one-dimensional motion with constant acceleration. Show that the power delivered to it at time‘t’ is proportional to‘t’. (1)
5. What is the moment of inertia of a rod of mass M, length l about an axis perpendicular to it through one end? (1)
6. Give the location of the centre of mass of a ring. Does the centre of mass of a body necessarily lie inside the body? (1)
7. Draw the position-time graph of an object moving with negative velocity. (1)
8. While considering the motion of an object under the gravitational influence of another object, which of the following quantities are conserved. (a) angular momentum (b) linear momentum (c) total mechanical energy (1)
9. The resistance R=V/I where V= (100 ±5) V, I= (10±0.2). Find the percentage error in R. (2)
10. Check the dimensional consistency of the equation. (2)
11. Fig shows the x-t plot of one dimensional motion of a particle. Is it correct to say from the graph that the particle moves in a straight line for t<0 and in a parabolic path for t>0? If not suggest a suitable physical context for this graph. (2)
12. The position of particle is given by r=3t î + 2t2ĵ + 5ǩ, where‘t’ is in seconds and the coefficients have proper units for ‘r’ to be in meters. Find V (t) and a (t) of the particle. (2)
13. What is impulse of a force, how it is related to momentum. (2)
14. The potential energy function for a particle executing linear simple harmonic motion is given by V(x)=kx2/2, where k is force constant of the oscillator. For k=0.5Nm-1 the graph of V(x) versus ‘x’ is as shown in figure. Show that a particle of total energy 1J moving under this potential must ‘turn back’ when it reaches ±2m.
OR
A body constrained to move along the Z-axis of a co-ordinate system is subject to a constant force F given by .What is the work done by this force in moving the body through a distance of 4m along the Z-axis? (2)
15. Prove work-energy theorem for a constant force. (2)
16. Define centre of gravity of a rigid body. (2)
17. What are the factors on which the moment of inertia of a body depends? (2)
18. Does the escape speed of a body from the earth depend on a) mass of the body b0 the height of the location of the body from where the body is launched? Justify . (2)
19. State Kepler’s laws of planetary motion. (3)
20. Explain the variation of acceleration due to gravity with a) altitude b)depth (3)
21. State i) theorem of parallel axes ii)theorem of perpendicular axes (3)
22. A pump on the ground floor of a building can pump water to fill a tank of volume30m3 in 15minutes.If the tank is 40m above the ground, and the efficiency of the pump is 30â„…, how much electric power is consumed by the pump? (3)
23. Explain why a) a horse cannot pull a cart and run in empty space b) a cricketer moves his hands backwards while holding catch. (3)
24. a) State Newton’s second law of motion.
b) A bullet of mass 0.04 kg moving with a speed of 90ms-1 enters a heavy wooden block and is stopped after a distance of 60cm.What is the average resistive force exerted by the block on the bullet? (3)
25. Two bodies are thrown with the same initial velocity at angles α and ( 90o-α) with the horizontal. What will be the ratio of i) maximum heights attained by them and ii) of horizontal ranges.
OR
What is a projectile? Show that the path of the projectile is parabolic. (3)
26. Explain any two uses of dimensional equations. Write any two of its limitations. (3)
27. A woman starts from her home at 9:00 am walks with a speed of 5km h-1 on a straight road up to her office 2.5 km away, stays at the office up to 5:00 pm and returns home by an auto with a speed of 25km h-1.Choose suitable scales and plot the x-t graph of her motion. (3)
28. a) What is uniform circular motion? Find the magnitude and direction of centripetal acceleration in case of uniform circular motion of an object.
OR
a) Find the magnitude and direction of the resultant of two vectors A and B in terms of their magnitudes and angle θ between them.
b) A motor boat is racing towards north at 25kmh-1 and the water current in that region is 10kmh-1 in the direction of 60o east of south. Find the resultant velocity of the boat. (5)
29. Obtain an expression for the potential energy of a spring and discuss the nature of its variation. Show that the total energy of the spring is constant in all positions. Show graphically the variation of PE, KE and TE with distance from the mean position.
OR
a) Answer the following questions with reasons:
i) In an elastic collision of two billiard balls, is the total kinetic energy is conserved during the short time of collision of the balls (i.e when they are in contact)?
ii) Is the total momentum is conserved during the short time of an elastic collision of two balls.
b) Give a brief account of elastic collision in two dimensions. (5)
30. a) Three bodies a ring ,a solid cylinder and a solid sphere roll down the same inclined plane without slipping. They start from rest. The radii of the bodies are identical. Which of the bodies reaches the ground with maximum velocity?
b) Given moment of inertia of a disc about any of its diameters to be MR2/4, find its moment of inertia about an axis normal to the disc and passing through a point on its edge.
c) Find the moment of the sphere about a tangent to the sphere, given moment of inertia of the sphere about any of its diameters to be 2MR2/5.
OR
a) Establish a relation between (i) torque and moment of inertia of a rigid body
(ii) Angular momentum and moment of inertia of a rigid body
b) A solid cylinder of mass20kg rotates about its axis with angular speed 100rad/s. The radius of the cylinder is 0.25m.What is the kinetic energy associated with rotation of the cylinder? What is the magnitude of angular momentum of the cylinder about its axis? (5)
******************************
How to get A in physics?Answer: Whatever the syllabus or course, an A grade means "Excellent work indicating a clear mastery of the subject material" This requires evidently a basic understanding of the subject, thorough with the fundamentals and the ability to apply the principles to solve problems creatively. One should be able to make suitable connections between concepts logically to solve the problem in hand. (Remember, Physics is often referred to as a Problem Solving Discipline) A grade in Physics comes naturally if you start loving the subject and take active interest in applying the concepts of Physics to solve problems (in subject as well as in day to day life situations) Also important :
"when a wave enters from air to water, its wavelength changes but frequency remains unchanged. why"Answer Velocity of a wave = frequency x time period V = ν λ When a wave travels from one medium to another, its velocity changes and so also is its wavelength, but frequency; which is the number of vibrations produced per second is independent of the medium, remains constant. However, their is a phenomenon called Doppler Effect where the apparent frequency (observed frequency) is different from actual frequency and is caused by the relative movement between the source and observer (listener) Got a better answer? Please post it as comment.
"What are limitations of principle of homogeneity of dimensional analysis?"The dimensional analysis has the following limitations
"How to solve rain and man problems from motion in one dimension?"Answer: The problem is solved using principles of vector addition. There is a simple logic to remember