Physics Class 11 Chapter 3 Notes

• Very important physics class 11 chapter 3 short questions and answers from Punjab Textbook.
• Definition of displacement 
• Definition of velocity
• Definition of Acceleration
• Velocity- Time Graph
• Review of equations of uniformly accelerated motion
• Newton's laws of motion
• Newton is the first law of motion
• Newton's second law of motion
• Newton's third law of motion
• Definition of momentum 
• Momentum and neutral in the second law of motion
• Definition of impulse
• Law of conservation of momentum
• Elastic and inelastic collision
• elastic collision in one dimension
• Force due to water flow
• Momentum and explosive forces
• Projectile motion
• Very important physics class 11 chapter 3 questions and answers pdf from Punjab Textbook.
• Height of the projectile
• time of flight
• Very important class 11 physics chapter 3 important numericals from Punjab Textbook.
• range of the projectile
• Rocket propulsion: Rockets move by expelling burning gas through engines at their rear. The ignited fuel turns to a high pressure gas which is expelled with extremely high velocity from the rocket engines (Fig. 3.15). The rocket gains momentum equal to the momentum of the gas expelled from the engine but in opposite direction. The rocket engines continue to expel gases after the rocket has begun moving and hence rocket continues to gain more and more momentum. So instead of travelling at steady speed the rocket gets faster and faster so long the engines are operating.
• A rocket carries its own fuel in the form of a liquid or solid hydrogen and oxygen. It can, therefore work at great heights where very little or no air is present. In order to provide enough upward thrust to overcome gravity, a typical rocket consumes about 10000 kgs of fuel and ejects the burnt gases at speeds of over 4000 ms. In fact, more than 80% of the launch mass of a rocket consists of fuel, only One way to overcome the problem of mass of fuel is to make the rocket from several rockets linked together.
• When one rocket has done its job, it is discarded leaving others to carry the space craft further up at ever greater speed.
• If m is the mass of the gases ejected per second with velocity v relative to the rocket, the change in momentum per second of the ejecting gases is mv. This equals the thrust produced by the engine on the body of the rocket. So, the acceleration 'a' of the rocket is a = mv/M.
• Very important class 11 physics chapter 3 short notes from Punjab Textbook.
• application of ballistic missiles: A ballistic flight is that in which a projectile is given an initial push and is then allowed to move freely due to inertia and under the action of gravity. An un-powered and un-guided missile is called a ballistic missile and the path followed by it is called ballistic trajectory.
• As discussed before, a ballistic missile moves in a way that is the result of the superposition of two independent motions: a straight line inertial flight in the direction of the launch and a vertical gravity fall. By law of inertia, an object should sail straight off in the direction thrown, at constant speed equal to its initial speed particularly in empty space. But the downward force of gravity will alter straight path into a curved trajectory. For short ranges and flat Earth approximation, the trajectory is parabolic but the dragless ballistic trajectory for spherical Earth should actually be elliptical. At high speed and for long trajectories the air friction is not negligible and some times the force of air friction is more than gravity. It affects both horizontal as well as vertical motions. Therefore, it is completely unrealistic to neglect the aerodynamic forces.
• The shooting of a missile on a selected distant spot is a major element of warfare. It undergoes complicated motions due to air friction and wind etc. Consequently the angle of projection can not be found by the geometry of the situation at the moment of launching. The actual flights of missiles are worked out to high degrees of precision and the result were contained in tabular form. The modified equation of trajectory is too complicated to be discussed here. The ballistic missiles are useful only for short ranges.
• Very important physics class 11 chapter 3 numericals pdf from Punjab Textbook.