1. Newton’s First Law & Linear Motion
The Review Game

2. What Did Galileo Observe From the Experiment Shown Below?
Inertia – a ball that doesn’t encounter the force of an inclined plane will go on forever until another force acts on it.

3. What force prevents the ball from rolling forever on Earth?
Friction!

4. An object’s resistance to changes in motion
So What is Inertia?
An object’s resistance to changes in motion
A property of matter!

5. What is Newton’s First Law?
An object either remains at rest or continues to move at a constant velocity, unless acted upon by an external force
AKA the law of inertia

6. What is a force? A push or a pull
Its source may be gravitational, electrical, magnetic, or simply muscular effort

7. What is net force?
When more than a single force acts on an object

8. What is the net force?
20 N
40 N
60 N
10 kg

9. What is the formula for mechanical equilibrium?

10. What does it mean for an object to be in mechanical equilibrium?
Everything not undergoing changes in motion is in mechanical equilibrium
This means ƩF=0

11. Can a moving object be in mechanical equilibrium?
YES!
All forces must be equal though
Throwing a ball in space - all forces equal

12. Can an object with a single force acting on it be in mechanical equilibrium?
All forces can’t be equal if there is only one acting on it

13. A book rests on a table. What 2 forces are acting on it?
Weight of the book
Normal force
Which is the upward (positive) and which is the downward (negative) force?
Weight of the book = downward, negative
Normal force = upward, positive

14. What keeps the Earth moving around the sun?
NOTHING!
Inertia says an object in motion will stay in motion

15. relative
Motion is ____________, meaning we describe it in relation to something else

16. A measure of the distance an object travels per unit of time
What is speed?
A measure of the distance an object travels per unit of time

17. How do you increase speed using the speed formula?
Decrease

18. What is instantaneous speed?
speed at a specific instant in time

19. What is the formula for average speed?

20. A car goes 3m in 4s, then 5m in 2s, then 8m in 2 seconds
A car goes 3m in 4s, then 5m in 2s, then 8m in 2 seconds. What is the car’s average speed?
2 m/s

21. What is velocity?
V= d/t WITH DIRECTION!

22. What is a vector?
Quantities that are fully described by both a magnitude and a direction.

23. Give 2 examples of a vector
Velocity
Force
Because they require both a magnitude (amount) and a direction

24. What is a scalar quantity? Give an example
Quantities that are fully described by a magnitude (or numerical value) alone
Speed

25. A constant velocity has a direction!
What is the difference between a constant speed and a constant velocity?
A constant velocity has a direction!

26. What is the definition of acceleration?
So we can change the velocity of something by changing its speed, direction or both
How quickly velocity changes is acceleration
What is the formula for acceleration?

27. A particular car can go from rest to 40 km/h in 10s
A particular car can go from rest to 40 km/h in 10s. What is its acceleration?
A = 40-0 / 10s = 4 km/h*s

28. Define a free falling object
When an object falls with no restraints (like friction with the air) and falls under the influence of gravity alone, the object is in a state of Free Fall
OR… fall with only the influence of gravity acting on the object

29. What is the official rate of acceleration due to gravity?
g = 9.8 m/s2

30. What is the formula for the velocity of a free falling object?
v = gt

31. A cat pushes a toy off of a deck
A cat pushes a toy off of a deck. The toy hits the ground 5 seconds later. What was the toy’s velocity before hitting the ground?
v = gt 49 m/s

32. How do we measure distance traveled of a falling object?
Distance traveled d = ½ gt2

33. We shot straws straight up into the air
We shot straws straight up into the air. We were able to find the height the straw went. How?
By timing the straw from v=0 (at the top of its fall) to the time it hit the ground.
We could then use the distance formula to find the distance formula
d = ½ gt2

34. So we know at the top of its path the straw is at a velocity of zero
So we know at the top of its path the straw is at a velocity of zero. What is the acceleration due to gravity at this position?
ALWAYS 9.8m/s2

35. A ball is thrown 125 meters upward and then falls the same distance back to Earth. Neglecting air resistance, its total time in the air is
10 seconds

36. An unfortunately clumsy small child falls off of a curb
An unfortunately clumsy small child falls off of a curb. It takes the child ¼ of a second to hit the ground. What is the child’s speed before hitting the ground?
v = gt
9.8 m/s2 *1/4 s
v= 2.45 m/s

37. What is the child’s average speed during the ¼ second?
Just find the average! /2
Average Speed = 1.23 m/s

38. How high is the ledge off of the ground?
Distance traveled d = ½ gt2
d = ½ * 9.8 m/s2 * (1/4)2
d=0.31m

39. What prevents objects from absolute free fall on Earth?
Air Resistance!