Worksheet #1 Physics for grade 9 I. Write true for the correct statement or false for the wrong statement. 1. For an object which is lifted up ward, work done by gravity is positive. 2. In the absence of external force momentum is conserved in any type of collision 3. During elastic collision total kinetic energy before collision is less than total kinetic energy After collision. 4. The inertia of an object depends on its mass. 5. Momentum takes the direction of velocity. 6. Friction always tends to act in the direction opposing motion. II. Match the column “A” with the similar concepts under column “B” “A” 11. Dynamic friction A. “B” Unit less Linear momentum B. Limiting friction 13. Impulse C. Change in momentum 14. Maximum value of static friction D. Mass x velocity 15. Coefficient of friction E. Kinetic friction F. Static friction 12 III. Among the given alternative choose the best answer 16. The unit of work may be expressed by _____________ A. N.m 2 B. kg. m s2 B. J D. All of the above 17. A force does a negative work when _____ A. The force is opposite to the displacement B. The force is perpendicular to the displacement C. Both the displacement and force are positive D. Both the displacement and force are negative 18. An object of mass m moving with velocity across a level surface comes to rest after traveling a distance d. what is the work done by friction? A. - Mvd B. 1 mv2 2 C. 1 1 2 mr d 2 D. Zero 19. In raising an object to a given height ‘h’ by means of inclined plane, as compared with raising the object vertically to the same height h, there is a reduction in A. Force required B. Work required C. Mechanical advantage D. distance pushed 20. A body having a mass m and kinetic energy KE. What is the momentum of the body? A. KE B. 2m 2KE M 2KE m C. D. 2m KE 21. Calculate the power developed by an athlete weighting 800N, When he runs up a staircase, climbing 20m in 4 seconds. A. 4 x 103 Watt B. 16 x 103Wat C. 10Watt D. 30Watt 22. A train is traveling at 20 m s along a straight level road. Its engine have a power out put of 800,000watt Find the force acting on the train? A. 40,000N B. 1600,000N C. 30,000N D. 70,000 23. In an elastic collision A. Momentum is not conserved. B. The kinetic energy before collision is greater than kinetic energy after collision C. Kinetic energy is conserved D. The kinetic energy before collision is less than kinetic energy after collision 24. If the velocity of an object is doubled, its kinetic energy is __________. A. Halved B. doubled C. quadrupled D. remain the same 25. Newton’s pairs of forces A. Are equal in magnitude B. Are opposite in direction C. Lie on the same line of action D. All are correct answers 26. A car of mass 4000kg is moving at 20m/s due south along a straight road. What is its linear momentum? A. 8 x104 kg m/s North C. 8 x 104 kg m/s South B. 8 x104 kg m/s East D. 8 x 104 kg m/s west 27. A bird flies by pushing air downwards. The air in turn pushes the bird upwards. Which of the The physics laws does the bird uses of fly? A. Law of conservation of energy 2 B. Law of gravity C. Newton’s third law D. Newton’s 1st law 28. An object of mass m moves with constant speed on a horizontal rough surface by the action of horizontal force of magnitude F. If the coefficient of kinetic friction is µk What is the magnitude of the acceleration when the force is removed? A. g B. k g C. µkg 2 D. 0 29. If an object is resting on an inclined plane A. The normal contact force is increased B. Frictional force is increased C. Weight increases D. there is component of the weight along the inclined plane 30. A block slides down a 370 frictionless inclined plane starting from rest at the top. Just up on reaching the bottom its velocity is 12m/s. What is the length of the inclined plane? (Sin370 =0.6 cos370 = 0.8, = 10m/s2 ) ( use law conservation of energy concept ) A. 12m B. 24m C. 6m d. 10m 31. A 2kg body is moving to the right with a velocity of 15m/s. It collides with a 1kg body which was at rest at the origin. After collision they stick together. Their velocity after collision is A. 5m/s B. 15m/s C. 10m/s D. 3m/s 32. The loss of kinetic energy after collision in the preceding question is A. 225J B. 37.5J C. 187.5J 33. In a closed system A. The total linear momentum will remain constant B. The total energy will remain constant C. The change in total linear momentum is zero D. All 34. A body is said to be under translational equilibrium. A. If it is at rest B. If it is moving with constant velocity C. If the vector sum of all forces acting on it is equal to zero D. All 35. Which of the following is a contact force? 3 D. 150J A. Gravitational force C. electric force B. Magnetic force D. gravitational force 36. An object of mass 40kg is found at a height of 10m, above the ground surface. What is the gravitational potential energy (take g = 9.8 m/s2) A. 3920J B. 2860J C. 9800J D. 4200J 37. A particle of mass m = 30gm, attached to a spring of force constant k = 200N/M is oscillating along the x – axis about the equilibrium position x = 0 as shown in fig below If the amplitude xmax = 10cm, what is the kinetic energy of the particle when it reaches the equilibrium position? A. 1000J B. 100J C. 1J D. 10J 38. A ball is thrown straight up. It rises for a while and drops back to the ground. Which of the following energy transformation best describe the process? A. Chemical B. Kinetic C. Potential D. Kinetic kinetic potential chemical potential kinetic potential potential kinetic IV. Fill the blank spaces 39. ____________ is the frictional force between two objects that are trying to move against each other but are not yet moving. 40. ____________ is the rate of doing work. 41. The SI unit of force is ____________ 42. In elastic collision both _______________ and ___________ are conserved. V. Work out (Use the space at the back of your answer sheet for your answer) 43. If a ball of mass m is released from point ‘A’ which is 80cm find the speed the ball at point B 44. Two balls of mass 1kg and 2kg moving towards each other with a speed of 2 m s and 6 m s 4 respectively collide each other. A. Find the velocity of each ball if the collision is perfectly inelastic B. Find the kinetic energy drop 45. A 1000kg car accelerates uniformly from 10m/s to 30m/s in 2seconds Find a. The change in momentum in this time b. Impulse c. Change in kinetic energy d. Work done e. Average power 5