11th Class Physics Chapter 4 Notes

Important Easy to understand 11th Class Physics Chapter 4 Notes Work and Energy written by Professor Mr. Asad Abbas Suib. These notes are very helpful in the preparation of class 11 physics chapter 4 exercise solutions for students of the 11th class and these are according to the paper patterns of all Punjab Book Boards.

Summary and Contents:
Topics which are discussed in the notes are given below:
  • Very Important Multiple Choice Questions class 11 physics chapter 4 mcq with answers with Answers of the Chapter No. 4: Work and Energy in 1st Year Physics Punjab Book Boards.
  • What is work? Calculate the Work done on constant force.
  • What is variable force? Calculate the work done by variable force.
  • What is gravitational field? Calculate the Work done by gravitational field.
  • What is Power? What is average and instantaneous power?
  • Define KWh. Prove that 1kwh=3.6 MJ.
  • What is Energy? define the types of energies.
  • State and explain Work Energy principle.
  • Important class 11 physics chapter 4 exercise questions from Punjab Textbook.
  • What is Absolute Potential Energy? Derive its relation.
  • What is Escape velocity? Derive its relation.
  • Explain Interconversion of potential energy and kinetic energy and Conservation of Energy.
  • In case of frictional force present during downward motion
  • What are Non-conventional Energy sources? Explain.
  • A person hold a bag of groceries while standing still, talking to a friend. A car is stationary with its engine running. From the standpoint of work, how are these two situations similar? 
  • Calculate the work done in kilo joules in lifting a mass of 10 kg (at a steady velocity) through a vertical height of 10 m.
  • In which case is more work done? When a 50 kg bag of books is lifted through 50 cm, or when a 50 kg crate is pushed through 2 m across the floor with a force of 50 N?
  • An object has 1 J of potential energy. Explain what it means? 
  • A ball of mass m is held at a height h1 above a table. The tabletop is at a height h2 above the floor. One student says that the ball has potential energy mgh1 but another says that it is mg (h1 + h2). Who is correct? 
  • When a rocket re-enters the atmosphere, its nose cone becomes very hot. Where does this heat energy come from?  
  • What sort of energy is in the following:
  • A girl drops a cup from a certain height, which breaks into pieces. What energy changes are involved?
  • A body uses a catapult to throw a stone, which accidentally smashes a greenhouse window. List the possible energy changes.
  • A man pushes a lawn mower with a 40 N force directed at an angle of  20 downward from the horizontal. Find the work done by the man as he cuts a strip of grass 20 m long.   
  • Important class 11 physics chapter 4 numericals pdf from Punjab Textbook.
  • A rain drop m =  3.35 10*-5 falls vertically at a constant speed under the influence of the forces of gravity and friction. In falling through 100 m, how much work is done by (a) gravity and (b) fiction. 
  • Ten bricks, each 6.0 cm thick and mass 1.5kg, lie flat on a table. How much work is required to stack them one on the top of another?
  • A car of mass 800kg travelling at 54kmh-1 is brought to rest in 60 meters. Find the average retarding force on the car. What has happed to original kinetic energy?
  • A 1000 kg automobile at the top of an incline 10 metre high and 100 m long is released and rolls down the hill. What is its speed at the bottom of the incline if the average retarding force due to friction is 480 N?
  • 100 m3 of water is pumped from a reservoir into a tank 10 m higher than the reservoir, in 20 minutes. If density of water is 100kg m-3, find (a) the increase in P.E. (b) the power delivered by the pump.
  • A force (thrust) of 400 N is required to overcome road friction and air resistance in propelling an automobile at 80kmh-1. What power (kW) must the engine develop?  
  • Important class 11 physics chapter 4 important numericals from Punjab Textbook.
  • A diver weighing 750 N dives from a board 10 m above the surface of a pool of water. Use the conservation of mechanical energy to find his speed at a point 5.0m above the water surface, neglecting air friction.
  • A child starts from rest at the top of a slide of height 4.0m. (a) What is his speed at the bottom if the slide is frictionless? (b) If he reaches the bottom, with a speed of 6 ms-1, what percentage of his energy at the top of the slide is lost as a result of friction? 

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