Monday, 11 June 2018

WORK AND ENERGY 9

Practice Paper  
Subject Physics (2020)
CH- 14  WORK AND ENERGY 
Class IX  

I. Very Short Answer Type Questions:
  1. Define work and energy. 
  2. When do we say that work is done?
  3. When is work done by a force zero? Is work have a direction?
  4. Define 1 joule of work.
  5. Write the expression for work.
  6. When the displacement of an object is perpendicular to the force acting on it. what is the work done by the force?
  7. Write the expression for the work done by the force when the displacement is made an angle with force.
  8. What is mechanical energy?
  9. Define potential energy with expression.
  10. What is elastic potential energy?
  11. How many watts in 1 horsepower?
  12. What is the commercial unit of energy? convert 1 kWh into j?
  13. What is the principle of conservation of energy?
  14. Does work have a direction?
  15. What is the relation between work and energy?
  16. What happens to the potential energy of a body when its height is doubled?
  17. If the speed of a body is halved, what is the change in its kinetic energy?
  18. What is the form of energy possessed by a running car?
  19. State value of a commercial units of electrical energy in Joules.
II. Short Answer Type Question:

  1. Work and energy are related to each other. Explain the given statement.
  2. If the angle between displacement and force acting on a particle is ∅. For which value of ∅ is the work done the minimum and maximum?
  3. Moon is experiencing a gravitational force due to earth and is revolving around the earth in a circular orbit. How much work is done by the moon?
  4. What is the work done against gravity when a body is moved horizontally along a frictionless surface?
  5. By what factor does the kinetic energy of a particle increase if the speed is increased by a factor of 3?
  6. A 40 kg girl is running along a circular path of radius 1 m with a uniform speed. How much work is done by the girl in completing one circle?
  7. A 2 m high person is holding a 25 kg trunk on his head and is standing at a roadway bus terminus. How much work is done? 
  8. A horse of mass 210 kg and a dog of mass 25 kg are running at the same speed. Which of the two possesses more kinetic energy?
  9. How many joules make one kilowatt-hour?
  10. When displacement is in a direction opposite to the direction of force applied, what is the type of work done?
  11. If the heart works 60 Joule in one minute, what is its power?
  12. Give the formula for calculating work done. What is the S.I unit of work?
  13. Define power and 1 watt of power. Write the S.I unit of power.
  14. Calculate the work done when a force of 15 N moves a body by  5 m in its direction.
  15. At what speed a body of mass 1 kg will have a kinetic energy of 1 J?
  16. What would be the amount of work is done on an object by a force if the displacement of the object is zero?
  17. How much work is done by a weight lifter when he held a weight of 80 kg on his shoulder for two minutes?
  18. A car and a truck are moving with the same velocity of 60 km/hr. Who has more kinetic energy?
  19. List two conditions that need to be satisfied for the work to be done on an object.
  20. A body is thrown vertically upwards. Its velocity goes on decreasing. Write the change in kinetic energy when its velocity becomes zero.
  21. What is the work done by the earth is moving around the Sun?

III. Long Answer Type Questions:
  1. The potential energy of a free-falling body decreases progressively. Does this violate the law of conservation of energy?
  2. Find the expression for the gravitational potential energy of a body of mass m at a height h.
  3. Find the expression for the kinetic energy of a body of mass m moving at a speed v.   
  4. What will be the kinetic energy of a body when its mass is made four times and velocity is double? Light and heavy objects have the same momentum. Find out the ratio of their kinetic energies. Which one has larger kinetic energy? 
  5. State the expression for the kinetic energy of a particle of mass m moving at a speed v.A rocket is moving up with a velocity v if the velocity of this rocket is suddenly tripled, what will be the ratio of two kinetic energies?
  6. Write the formula or expression for the change in kinetic energy of a body of mass which experiences a change in its velocity from u m/s to v m/s when force is applied on it. 
  7. Define kinetic energy. A horse of mass 200 kg and a dog of mass 20 kg are running at the same speed. Who h of the two possesses more kinetic energy?
    (i) What is the S.I unit of kinetic energy? What is the kinetic energy of a body of mass moving with a velocity of 4 m/s?
    (ii) A freely falling body eventually stops on the ground. What happens to its kinetic energy on the ground?  
  8. The kinetic energy of an object of mass ('m')moving with a velocity of 5 m/s is 25 J . Calculate its kinetic energy when its velocity is double.
  9. Write the form of energy possessed by the object in the following situation
    (i) a coconut falling from the tree.
    (ii) an object raised to a certain height.
    (iii) blowing wind.
    (iv) a child driving a bicycle.
  10. Given below are a few situations, study them and state in which of the given cases work is said to be done. Give reasons for your answer.
    (i) A person pushing hard a huge rock does not move
    (ii) A bullock pulling a cart up to 1 km on road.
    (iii) A girl pulling a trolley for about 2 m distance.
    (iv) A person standing with a heavy bag on his head.
  11. An object was thrown at a certain angle from the ground moves in a curved path and falls back to the ground. The initial and the final points of the path of the object lie on the same horizontal line. 
    (i) What is the work done by the force of gravity on the object?
    (ii) How is work done by a force measured? A porter lifts luggage of 20 kg from the ground and puts in on his head 1.7 m above the ground. Find the work done by the porter on the luggage?
  12. A box about 10 kg is placed at a point A on a horizontal surface. It is raised to a point B which is just at a distance of 2 m above A. Find the work done against by the force of gravity on the box. Justify your answer. ( g=10 m/s).
  13. An archer stretched a bow to release an arrow to hit the target at a distance of 10 m. Explain who does the work. In which form is the energy possessed by the bow and the arrow?     
  14. A body of mass 2 kg is thrown up with a speed of 25 m/s. Find the maximum potential energy.
  15. What is the work to be done to increase the velocity of a car from 30 km /hr to 40 km/hr, if the mass of the car is 1500 kg?
  16. A bag of wheat 60 kg. Find the height to which it is lifted so that its potential energy is 3000 J. ( g= 10 m/s).
  17. When will be work positive, negative or zero? Explain with examples.
  18. Write the names of four different forms of energy and give an example where energy is transformed from one form to another? 
  19. A 5 kg ball is thrown upward with a speed of 10 m/s.
    (i) Calculate the maximum height attained by it.
    (ii) Find the potential energy when it reaches the highest point. 
NCERT QUESTIONS:
  1. When do we say that work is done?
  2. Write an expression for the work done when a force is acting on an object in the direction of its displacement.
  3. Define 1 J of work.
  4. A pair of bullocks exerts a force of 140 N on a plough. The field being ploughed is 15 m long. How much work is done in ploughing the length of the field?
  5. What is the kinetic energy of an object?
  6. Write an expression for the kinetic energy of an object.
  7. The kinetic energy of an object of mass, m moving with a velocity of 5 m s–1 is 25 J. What will be its kinetic energy when its velocity is doubled? What will be its kinetic energy when its velocity is increased three times?
  8. What is power?
  9. Define 1 watt of power.
  10. A lamp consumes 1000 J of electrical energy in 10 s. What is its power?
  11. Define average power.
  12. Look at the activities listed below. Reason out whether or not work is done in the light of your understanding of the term ‘work’.
    (i) Suma is swimming in a pond.
    (ii) A donkey is carrying a load on its back.
    (iii) A windmill is lifting water from a well.
    (iv) A green plant is carrying out photosynthesis.
    (v) An engine is pulling a train.
    (vi) Food grains are getting dried in the sun.
    (vii) A sailboat is moving due to wind energy.
  13. An object was thrown at a certain angle to the ground moves in a curved path and falls back to the ground. The initial and the final points of the path of the object lie on the same horizontal line. What is the work done by the force of gravity on the object?
  14. A battery lights a bulb. Describe the energy changes involved in the process.
  15. A certain force acting on a 20 kg mass changes its velocity from 5 m s–1 to 2 m s–1. Calculate the work done by the force.
  16. A mass of 10 kg is at a point A on a table. It is moved to a point B. If the line joining A and B is horizontal, what is the work done on the object by the gravitational force? Explain your answer.
  17. The potential energy of a freely falling object decreases progressively. Does this violate the law of conservation of energy? Why?
  18. What are the various energy transformations that occur when you are riding a bicycle?
  19. Does the transfer of energy take place when you push a huge rock with all your might and fail to move it? Where is the energy you spend going?
  20. A certain household has consumed 250 units of energy during a month. How much energy is this in joules?
  21. An object of mass 40 kg is raised to a height of 5 m above the ground. What is its potential energy? If the object is allowed to fall, find its kinetic energy when it is half-way down.
  22. What is the work done by the force of gravity on a satellite moving round the earth? Justify your answer.
  23. Can there be displacement of an object in the absence of any force acting on it? Think. Discuss this question with your friends and teacher.
  24. A person holds a bundle of hay over his head for 30 minutes and gets tired. Has he done some work or not? Justify your answer.
  25. An electric heater is rated 1500W. How much energy does it use in 10 hours?
  26. Illustrate the law of conservation of energy by discussing the energy changes which occur when we draw a pendulum bob to one side and allow it to oscillate. Why does the bob eventually come to rest? What happens to its energy eventually? Is it a violation of the law of conservation of energy?
  27. An object of mass, m is moving with a constant velocity, v. How much work should be done on the object in order to bring the object to rest?
  28.  Calculate the work required to be done to stop a car of 1500 kg moving at a velocity of 60 km/h?
  29. In each of the following a force, F is acting on an object of mass, m. The direction of displacement is from west to east shown by the longer arrow. Observe the diagrams carefully and state whether the work done by the force is negative, positive or zero. 
  30. Soni says that the acceleration in an object could be zero even when several forces are acting on it. Do you agree with her? Why?
  31. Find the energy in kWh consumed in 10 hours by four devices of power 500W each.

at
Labels: ,

No comments:

Post a Comment

Subscribe to: Post Comments (Atom)