Class 11 Physics Ch 3 Notes

• Important from class 11 physics ch 3 important questions Punjab Textbook.
• Define the terms (i) Displacement (ii) Velocity (iii) Instantaneous velocity (iv) Average velocity (v) Uniform velocity.
• Define the terms (i) Acceleration (ii) Instantaneous acceleration (iii) Positive acceleration (iv) Negative Acceleration.
• Define Newton’s law. Ans: Newton’s first law of motion: A body at rest remain at rest and a body moving with uniform velocity will continue to do so, unless unbalanced external force acts on it. Newton’s 2nd Law of motion: "When a net force acts on a body, it produces acceleration in the body in the direction of the net force. The magnitude of this acceleration is directly proportional to the net force acting on the body and inversely proportional to its mass." F = ma.
• How do you find the momentum of an explosive force? Explain with one example. Ans: When a shell explodes in mid-air, its fragments fly off in different directions. The total momentum of all its fragments equals the initial momentum of the shell. Suppose a falling bomb explodes into two pieces. The momentum of the bomb fragments combines by vector addition equal to the original momentum of the falling bomb. 
• Show that the area between the velocity time graph is equal to the distance covered by the object.
• Define Inertial frame of reference.
• Define momentum, Write its formula and unit.
• Define isolated with suitable example.
• State law of conservation of momentum. Write its formula.
• Drive the relation for force due to water flow.
• How do you find the momentum of an explosive force? Explain with one example.
• When a bullet is fired from a riffle. Why does the riffle move backward?
• What is principle of rocket propulsion?
• Define ballistic missile, ballistic flight and ballistic trajectory.
• Why a safety of a motorcycle’s is padded? 
• What is the difference between uniform and variable velocity? From the explanation of variable velocity, define acceleration. Give SI units of velocity and acceleration.  
• An object is thrown vertically upward. Discuss the sign of acceleration due to gravity, relative to velocity, while the object is in air?
• Can the velocity of an object reverse direction when acceleration is constant? If so, given an example?
• Can the velocity of an object reverse direction when acceleration is constant? If so, given an example?
• Find the change in momentum for an object subjected to a given force for a given time and state law of motion in terms of momentum?
• Important from class 11 physics chapter 3 important questions with answers pdf Punjab Textbook.
• Define impulse and show that how it is related to linear momentum?
• Can the velocity of an object reverse direction when acceleration is constant? If so, given an example? Ans: Yes, it is possible. Example: - When a body is thrown vertically upward, its velocity decreases because of downward force of gravity and becomes zero at the highest point and the body starts moving downward and reverses its direction of velocity, but the acceleration remains constant during whole flight.
• State the law of conservation of linear momentum, pointing out the importance of isolated system. Explain, why under certain conditions, the law is useful even though the system is not completely isolated?
• Explain the difference between elastic and inelastic collision. Explain how would a bouncing ball behave in each case? Give plausible reasons for the fact that K.E is not conserved in most cases?
• At what point or points in its path does a projectile have its minimum speed, its maximum speed? 
• Important from class 11 physics chapter 3 short questions Punjab Textbook.