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Newton’s Laws & Universal Law of Gravitation

  1. A racing car weighs 6958 N. What is its mass? If it starts from rest and travels 12 m in 2 sec, what is its acceleration? What net force caused this acceleration? Ans: 710 kg; 6 m/s2, 4260 N
  2. An 8 kg ball is separated from a 6 kg ball by 2 m. What is the gravitational force of attraction between them? Ans: 8 x 10-10 N
  3. Two satellites of equal mass are put into 30 m apart. A gravitational force of 2 x 10-7 N acts between them. What is the mass of each satellite? What is the initial acceleration given each satellite by this force? Ans: 1643 kg; 1.22 x 10-10 m/s2
  4. A rubber ball weighs 49 N. It is thrown upward with a force of 69 N. What is the net force? What acceleration does it cause? Ans: 20 N; 4 m/s2
  5. An object with a mass of 22.7 kg is placed on a horizontal surface. The mass moves horizontally at constant speed. The coefficient of friction between the two surfaces is 0.94. What is the force of friction? Ans: 209.11N
  6. It takes 50 N to pull a 6 kg object along a desk at constant speed. What is the coefficient of friction? Ans: 0.85
  7. A boy pushes horizontally on a 10 kg wagon and it accelerates at 2.5 m/s2. If frictional forces total 50 N, what force is he exerting on it? Ans: 75 N
  8. The mass of an elevator plus occupants is 752 kg. The tension in the cable supporting the elevator is 8950 N. What is the net force? What is the elevator’s acceleration? Ans: 1580.4 N; 2.10 m/s2
  9. A pulley holds a 10 N weight. A man pulls on the rope with an upward force of 15 N. What acceleration does the weight experience? Ans: 4.90 m/s2
  10. A 800 N force pushes a 50 kg block horizontally on a table. The coefficient of friction between the surfaces is 0.60. What force of friction opposes the motion? What is the net force? What is the block’s acceleration? Ans: 294 N; 506 N; 10.12 m/s2
  11. A bicycle with a mass of 3.1 kg feels a frictional force of 21 N retarding its motion. A 50 N force is applied by the bicyclist on the wheel. What is the coefficient of friction between the bicycle and the road. What acceleration does it experience? Ans: 0.69; 9.35 m/s2
  12. A 20 kg block is pulled along a horizontal surface by a 50 N force exerted along an attached rope making a 35° angle with the horizontal. What is the normal force exerted by the surface to support the box? If the block is pulled at a constant speed, what is the coefficient of friction between the surfaces? Ans: 167.32 N; 0.24
  13. What is the normal force and the coefficient of friction if the block in number twelve is now pushed at constant speed? Ans: 224.68 N; 0.18
  14. If the coefficient of friction between the two surfaces in number twelve was 0.15, what would be the acceleration of the block? Ans: 0.79 m/s2
  15. Find the normal and the parallel forces for the following: a) a 14 N object rests on a 28° slope and b) a 1.4 kg object rests on a 28° slope. Ans: a) 12.36 N, 6.57 N; b) 12.11 N, 6.44 N
  16. A 30 N block slides down a 35° incline with constant speed. What is the frictional force? What is the coefficient of friction between the surfaces? Ans: 17.21 N; 0.70
  17. A 6 N object is pushed up a 22° incline at constant speed by a 6 N force. What is the frictional force? What is the coefficient of friction? Ans: 3.75 N; 0.67
  18. An 8 N object is pushed up a 23° slope with an acceleration of 1 m/s2 by a 10 N force. What is the coefficient of friction between the surfaces? Ans: .82
  19. A 12 N object slides down a 15° incline with an acceleration of 1.8 m/s2. What is the coefficient of friction between the surfaces? Ans: 0.08
  20. A picture weighing 1000 N hangs suspended from a two wires. At the point of attachment to the picture, each wire makes a 70° angle with the vertical. What is the tension in each wire? Ans: 1461.90 N
  21. A 1000 N traffic sign is held by two wires connected to two poles. One wire forms an angle of 30° with the horizontal and the other an angle of 60° with the horizontal. What is the tension in each wire? Ans: 500 N; 866 N
  22. A 500 N sign is held by two wires connected to two poles. One wire is attached horizontally (in other words, it makes an angle of 0° with the horizontal). The other makes an angle of 40° with the horizontal. What is the tension in each wire? Ans: 596 N; 778 N

Newton's Laws Notes

Newton's Laws Sample Problems