Speed of Light and Protons
If the definition of the speed of light is for massless particles, then how is a proton, having mass, accelerated to the speed of light? This sounds like a conumdrum.
Posted Thierence
Answer:
No massive particle has not so far crossed the speed of light. Even the extremely light particles – the neutrinos – couldnot cross the speed of light. Protons have not crossed the speed of light. When it nears the speed of light, the relativistic mechanics will become prominent and the it is to be treated is different from the classical mechanics.
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Categories: Ask Physics, CBSE PHYSICS CLASS XI, Interesting Questions, Relativity Tags: Alternative, black hole, Classical mechanics, Internet forum, physics, relativity, Special relativity, wikipedia
Body at incline
1. In first case we have the box with weight, say, 10 Newtons on incline. We calculate two components (perpendicular and parallel)of weight. We calculate normal force and force of friction. The box is at rest.
2. In second case we have ball on incline, made of same material as box from first case. Weight of the ball is the same as in first case, components of weight are the same as in first case. Normal force and friction have the same amount as in the case of box. But,unlike the box, ball is moving – it slides down. How’s that possible? If calculated net force is zero?
Petar asked
Answer:
It is not true that the ball slides, but it will roll down.
In the first case, the forces balance each other and there is no motion.
In the second force, the frictional force acting tangentially backwards (up the incline) and the component of weight of the ball acting parallel to the plane and through the centre of the ball constitute a couple and tends to rotate it. Now there is no sliding; it rolls.
(If any further clarification is required please post as comment to this post)
Please refer to http://www.real-world-physics-problems.com/rolling-without-slipping.html for detailed treatment of the Physics of rolling without friction.
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Categories: Ask Physics, CBSE PHYSICS CLASS XI, Interesting Questions Tags: friction, gravitation, Health, India, Indian mathematics, Mathematics, Net force, Newton, Newton's laws of motion, Normal force, Shopping, Veda, weight, Weight Loss
Doubts from Physics for Class XI – Collisions, Spring Constant, Gravitation, Measurement
- A billiard ball A moving with an initial speed of 1 m/s, undergoes a perfectly elastic collision with another identical ball B at rest. A is scattered through an angle of 30˚. What is the angle of recoil of B? What is the speed of ball A after the collision?
- Two springs have force constants K1 and K2 (K1> K2).On which spring is more work will be done if : (i) when they are stretched by the same force? and (ii) they are stretched through the same distance?
- Show that the acceleration of free fall g at the surface of earth and the gravitational constant G are related by the expression
g = 4\3 Π p G R,
- The radius of curvature of a concave mirror ,measured by a spherometer ,is given by
R = l2 /6h + h/2 The value of l and h are 4.0 cm and 0.065 cm respectively, where l measured by a meter scale and h by a spherometer.Find the error in the measurement of R.
Categories: CBSE PHYSICS CLASS XI Tags:
CLASS 11 – HALF YEARLY EXAMINATION SAMPLE PAPER -1
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 Read more…
