7th Grade
Chapter 23: Newton’s Laws of Motion NOTES
TEST 4/18/12
Section 1: Motion
1. Motion is a change in position.
2. Distance is the entire path an object travels.
3. The distance and direction between starting and stopping positions is displacement.
4. Relative motion is an object’s position change is described in terms of a reference point.
5. Speed is the distance traveled divided by the time needed to travel the distance, or speed =
6. Constant speed is speed that is the same at any given moment in time.
7. Speed at a particular instant in time is instantaneous speed.
8. Velocity is displacement divided by time, or velocity =
9. The velocity formula calculates average velocity. (doesn’t take in to consideration acceleration)
10. Velocity also includes direction, not just speed. Ex. Speed 60 mph, velocity 60 mph southeast
11. Change in velocity divided by the time required for the change to occur is acceleration.
12. Acceleration occurs when an object slows down as well as speeds up.
13. For an object traveling in a straight line, a change in speed can be used to calculate acceleration.
14. Acceleration is the final speed minus initial speed divided by time, or acceleration =
15. Initial speed is always zero for an object that started at rest. (not moving)
16. Turning or changing direction is also acceleration.
Section 2: Newton’s First law
17. Laws of motion are sets of rules first state by Isaac Newton.
18. Force is a push or pull with a size and direction.
19. Contact forces involves objects touching each other.
20. Long-range forces include gravity, magnetism, and electricity.
21. When scientists measure force, they use the newton, abbreviated N.
22. First law of motion states that an object will remain at rest or move in a straight line with constant speed unless a force
acts on it.
23. Inertia measures an object’s tendency to remain at rest or keep moving.
24. Inertia is related to mass; objects with more mass have more inertia.
25. Sometimes more than one force acts on an object.
26. Balanced forces are forces that are equal but in opposite directions, canceling each other.
27. If one force is greater than another, a change in motion will result from the unbalanced forces.
Section 3: Second Law of Motion
28. Second law of motion states than an object acted on by an unbalanced force will accelerate in the direction of the force.
29. Acceleration equals force divided by mass, or acceleration =
30. Force is equal to the combination of all forces, or the total force that acts on an object.
31. Second law can also be used to find force if mass and acceleration are known.
32. Near Earth’s surface, the force of gravity causes all objects to fall with the same acceleration – 9.8 m/s2
33. For any object that is falling, the force of gravity equals mass times acceleration due to gravity, or
Force = mass x (9.8 m/s2)
34. Because weight is the force of gravity on an object, an object’s weight equals mass times acceleration due to gravity, or
weight = mass x (9.8 m/s2)
35. Weight and mass are not the same thing.
36. Weight changes when the acceleration due to gravity changes.
37. Mass remains the same no matter what weight is.
38. Friction is a force that resists motion and is always present between two moving surfaces.
7th Grade
Chapter 23: Newton’s Laws of Motion NOTES
TEST 4/18/12
39. Static friction keeps a stationary object from moving on a surface
40. Sliding friction occurs when two surface slide past each other; slows down the moving object.
41. Rolling friction is friction between a surface and a wheel when the wheel rolls over the surface.
42. Air resistance is typical action of air molecules on a forward-moving object, slowing its motion.
Section 4: Newton’s 3rd Law
43. Third law of motion states that forces always act in equal but opposite pairs.
44. When a force is exerted on an object, the object exerts the same amount of force.
45. Third law of motion applies whether forces are contact or long-range.
46. Things move because action and reaction forces work on different objects.
47. Friction is a factor in the third law.
48. Using the second law equation, the object with the larger mass has the smaller acceleration if the same force is applied.
49. All objects in the universe exert a force on all others; however, differences in mass may make these forces
unnoticeable.
50. The three laws of motion describe how any objects moves when forces act on it.
51. Another way to state the 3rd law, is that for every action there is an equal and opposite reaction.
52. Another way to state the 2nd law, is that acceleration is produced when a force acts on a mass. The greater the mass (of
the object) the more force needed (to accelerate the object).
53. Another way to state the 1st law, is that an object at rest tends to stay at rest, and an object in motion tends to stay in
motion.