Momentum e

1. If a net force is exerted on an object, the object will accelerate in the direction of the force. The acceleration is directly proportional to the force and inversely proportional to the mass of the object. 2. An object will remain in a state of rest, or motion with a constant velocity in a straight line, unless a resultant force is exerted on it. 3. If object A exerts a force on object B, object B will exert a force of the same magnitude on object A, but in the opposite direction. 4. Newton I:Newton II: Newton III: = = Opposite directions = 0 if = 0 1 = = 0 2 5. The product of the mass and velocity. 6. Symbol: Unit: kgms-1 Vector = 7. Hoe has the most momentum? 8. Represent both Santa and his elfs a) velocity and b) momentum with vector diagrams. 9. Has the same shape as the velocity-time graph Example: An object is push with a constant net force. Draw a freehand momentum- time graph. 10. = = = ( ) = NB! CHANGE = FINAL - INITIAL 11. The change in momentum. The product of the force and the time that it is exerted on the object. 12. Symbol: Unit: Ns Vector 13. = = Impulse ON an object = Change in momentum OF the object 14. () () Force on ball changes as it deforms 15. () () = = 16. a) Prove that: = = b) Prove that: = 1 17. Give one word for the following definition: The rate of change in momentum Answer: Net (Resultant) Force 18. A 200 g tennis ball hits a wall perpendicularly with a velocity of 12 ms-1 and bounces beck with a velocity of 9 ms-1. 12 ms-1 9 ms-1 19. a) Determine the impulse on the ball. b) Calculate the force that the wall exerts on the ball if the collision lasts 0,02 s? c) What is the force that the ball exerts on the wall? d) Present the change in momentum with a vector diagram. 20. They dont make em like they used to Discuss the safety of modern cars during collisions by referring to force, momentum and impact time. 21. a) Crumple zone: As the car crumples, it increases the time during which the impact is absorbed. The change in momentum remains constant. 1 If t increases, decreases. 22. b) Airbags: When the airbags deploy, it increases the time for the occupants to come to rest The change in momentum remains constant. 1 If t increases, decreases. 23. Question: Why do rock climbers use elastic nylon ropes? 24. Antwoord: Wanneer hulle val, rek die tou uit en verleng sodoende die impak tyd Die verandering in momentum bly konstant 1 As t toeneem, neem af 25. Discuss why the egg survived in each of the cases. 26. Explain the phenomenon using your knowledge of impulse, momentum en Newton I. 27. A portion of the physical universe chosen for analysis. Isolated system: A system on which no external forces (eg. friction) is exerted. 28. The total linear momentum in an isolated system remains constant in magnitude and direction Used for the analysis of Collisions and Explosions 29. = 1 1 + 2 2 = 1 1 + 2 2 30. A collision is elastic if the total kinetic energy of the system is conserved. Use if: Collision is completely elastic To determine if collision is elastic 31. = 1 2 1 1 2 + 1 2 2 2 2 = 1 2 1 1 2 + 1 2 2 2 2 32. Momentum is coserved Kinetic Energy is conserved 33. 6 1 2 1 3 1 ? ? ? ? A ball with mass 4 kg rolls to the right with a velocity of 6 ms-1 and collides with another ball (8 kg) rolling to the left with a velocity of 2 ms-1. After the collision the 2 kg ball moves to the right at 3 ms-1 . 34. a) Determine the magnitude and direction of the velocity of the 4 kg ball after the collision. b) Determine the change in momentum of the 4 kg ball. c) Determine the magnitude and direction of the force exerted on the 4 kg if the collision lasts 0,02 s. d) Without a calculation, state the magnitude and direction of the force exerted on the 8 kg ball. e) Is the collision elastic? Prove with a calculation. 35. 2 1 6 1? ? ? ? Two fully loaded train trucks move to the right at 2 ms-1. A small explosive charge causes the trucks to separate so that truck B (mass 2 ton) moves further right at 6 ms-1. Calculate the new velocity of truck A if it has a mass of 3 ton. 36. A man with a mass of 87 kg on roller skates move with a constant velocity in a straight line when he sees a boy (mass 22 kg) standing in his direct path. When he collides with the boy, he grabs hold of the boy and together they move further with a velocity of 2,4 ms-1 in a straight line. a) Calculate the velocity of the man just before the collision. b) Is the collision elastic? Prove your answer with a calculation. 37. The boy and the man continues to move with a velocity of 2,4 ms-1 until they reach a gravel road. They move a further 2 m on the gravel road before the come to rest. c) Calculate the force that the gravel exerts on the man and the boy.