# ch 3 & 4

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1. what is Newton's first law of motion?
an object at rest will remain at rest and an object in motion will continue moving at a constant velocity unless acted upon by a net force
2. change in position in relation to a reference point
motion
3. speed
• rate of motion
• distance traveled per unit of time
4. calculation of speed
speed = distance/time
5. Sound travels 330 m/s. If a lightning bolt strikes the ground 1 m away from you, how long will it take for you to hear it?
330 s
6. Your friend skates at a speed of 4 m/s. You can skate 100 m in 20 s. Who skates faster?
you do
7. speed at a given instant
instantaneous speed
8. average speed equals?
total distance/total time
9. speed that doesn't change over time
constant speed
10. speed that is not constant
changing speed
11. speed in a given direction
velocity
12. can velocity change even when the speed is constant?
yes
13. distance and direction of an object's change of position from a starting point
displacement
14. a runner runs a distance of 50 m in one direction and then 30 m in the opposite

displacement = ?
20 m
15. acceleration
• the rate of change of velocity
• change in speed or direction
16. positive acceleration
speeding up
17. negative acceleration
slowing down
18. A roller coaster starts down a hill at 10 m/s. Three seconds later, its speed is 32 m/s. What is the roller coaster's acceleration?
7.3 m/s2
19. how long will it take a car traveling 30 m/s to come to a stop if its acceleration is -3 m/s2?
10 s
20. slope = ?
speed
21. straight line on a graph?
constant speed
22. flat line on a graph?
no motion
23. steeper slope on a graph?
faster speed
24. how is acceleration indicated on a distance-time graph?
by a curve
25. changing slope = ?
changing velocity
26. acceleration occurs when an object's ___ changes
speed
27. when an object speeds up, it has ___ acceleration
positive
28. when an object's final velocity is less than its initial velocity, it has ___ velocity
negative
29. formula for acceleration?
A = Vf - Vi /T
30. ___ is always on the X-axis
time
31. the further to the right, the ___
longer time
32. ___ is always on the Y-axis
distance
33. the higher up the graph, the ___
further we are
34. what does a horizontal line on a distance-time graph indicate?
something isn't moving
35. what does a straight line with a positive slope indicate?
36. when the motion of 2 objects is plotted on the same graph, how can you tell which one has the greater speed?
steeper incline
37. how do you tell if the speed of an object is constant?
38. what does the horizontal line on a speed-time graph indicate?
constant speed
39. what is the Y-axis on a speed-time graph?
speed
40. what does a straight line with a positive slope indicate?
acceleration
41. what does a straight line with a negative slope indicate?
acceleration
42. when the speed of 2 objects is plotted on the same graph, how can you tell which one has the greater acceleration?