1. Applied Lab Physics Mrs. Campbell
Chapter 7 Motion
Applied Lab Physics
Mrs. Campbell

2. Ch. 7, Lesson 1 What are Motion and Speed?
Motion - A change in position.
Elapsed time - The length of time that passes from one event to another.
Speed - The rate at which the position of an object changes.
Distance - The length of the path between two points.

3. Ch. 7, Lesson 1 What are Motion and Speed?, con’t
Example: Calculating Elapsed Time
Your flight began at 8:00 PM and ended at 11:00 PM. How long did your flight take?
Elapsed Time = Arrival Time – Departure Time
11:00 PM – 8:00 PM =
3 hours

4. Ch. 7, Lesson 1 What are Motion and Speed?, con’t
Practice Problem: Calculating Elapsed Time
Your flight began at 7:00 PM and ended at 9:00 PM. How long did your flight take?
Elapsed Time = Arrival Time – Departure Time
Elapsed Time = 9:00 PM – 7:00 PM
Elapsed Time = 2 hours

5. Ch. 7, Lesson 1 What are Motion and Speed?, con’t
Example: Calculating Average Speed
An airplane travels 810 miles in 3 hours. What is the average speed of the airplane?
Average speed = Distance Time
Average speed = 810 miles hours
Average speed = 270 miles
1 hour
The average speed of the airplane is 270 miles per hour.

6. Ch. 7, Lesson 1 What are Motion and Speed?, con’t
Practice Problem: Calculating Average Speed
An airplane travels 1230 miles in 5 hours. What is the average speed of the airplane?
Average speed = Distance Time
Average speed = 1230 miles hours
Average speed = 246 miles hour
The average speed of the airplane is 246 miles per hour.

7. Ch. 7, Lesson 1 What are Motion and Speed?, con’t
Calculating Distance – knowing speed and time we can calculate distance with the formula
Distance = speed x time
Example – If you can travel 50 miles per hour and you travel for 6 hours, what is the distance traveled?
Distance = 50 miles x 6 hours
1 hour
Distance = 300 miles

8. Ch. 7, Lesson 1 What are Motion and Speed?, con’t
Practice Problem - Calculating Distance
If a car travels 60 kilometers per hour and travels for 7 hours, what is the distance traveled?
Distance = 60 km x 7 hours
1 hour
Distance = 420 km

9. Ch. 7, Lesson 1 What are Motion and Speed?, con’t
Calculating Time – knowing distance and speed we can calculate the time it will take to travel that distance.
Time = distance speed

10. Ch. 7, Lesson 1 What are Motion and Speed?, con’t
Example – Calculating Time
You have a job marking lines on a sports field. The distance to be marked is 80 meters. You mark at the speed of 50 meters per minute. How much time will it take to mark the line?
Time = distance speed
Time = 80 meters
50 meters per minute
Time = 1.6 minutes

11. Ch. 7, Lesson 1 What are Motion and Speed?, con’t
Practice Problem – Calculating Time
A car went 70 miles at an average speed of 60 miles per hour. How long did it take to travel the 70 miles?
Time = distance speed
Time = 70 miles
60 miles per hour
Time = = 1.17 hours

12. Ch 7, Lesson 2 Using a Graph to Describe Motion
Constant Speed – Speed that does not change.
On a graph, constant speed is shown by a straight line.
Distance (km)
Time (hrs)
Graph showing constant speed

13. Ch 7, Lesson 2 Using a Graph to Describe Motion
Velocity – the speed and direction in which an object is moving.
Example of Velocity – 200 m in 7 seconds, east.

14. Ch 7, Lesson 2 Using a Graph to Describe Motion
Varying Speed – Speed that is not constant.
On a graph, varying speed will be shown by a non-straight line
Distance (km)
Time (hrs)
Graph showing varying speed

15. Ch 7, Lesson 2 Using a Graph to Describe Motion
Using a Graph to Find Unknown Distances
We can use a graph for constant speed to find an unknown distance or time.

16. Ch 7, Lesson 2 Using a Graph to Describe Motion
Using a Graph to Predict Distances
We can use a graph for constant speed to predict a distance that is not on the graph.

17. Ch 7, Lesson 3 Acceleration
Acceleration – the rate of change in velocity.
Acceleration = Change in velocity
Change in time
Change in velocity = final speed – original speed
Change in time = end time – start time

18. Ch 7, Lesson 3 Acceleration
Acceleration – Example Problem
A car starts from a stopped position. After 5 seconds, it has a speed of 40 km/hr. What is the car’s acceleration?
Acceleration = Change in velocity
Change in time
Acceleration = 40 km/hr
5 second
Acceleration = km/hr per second

19. Ch 7, Lesson 3 Acceleration
Deceleration – a form of acceleration used for the rate of slowdown.
Deceleration is indicated by a negative (-) number or by using the word deceleration.

20. Ch 7, Lesson 3 Acceleration
Example Problem – A car is traveling at 20 km/hr. The driver suddenly puts on the brakes. The car comes to a complete stop 4 seconds later. What is the rate of acceleration?
Acceleration = Change in velocity
Change in time
Acceleration = 0 km/hr – 20 km/hr
4 sec
Acceleration = -20 km/hr
Acceleration = -5 km/hr/sec
or the vehicle decelerated at 5 km/hr/sec

21. Ch 7, Lesson 3 Acceleration
Practice Problem – Acceleration
A car starts from a stopped position. After 8 seconds, the car has a speed of 40 km/hr. What is the car’s acceleration?
Formula Acceleration = Change in velocity
Change in time
A = 40 km/hr – 0 km/hr
8 sec – 0 sec
A = 40 km/hr
8 sec
Acceleration = 5 km/hr/sec

22. Ch 7, Lesson 4 The Laws of Motion
Sir Isaac Newton (1643 – 1727) was an English scientist and mathematician.
He is famous for his discovery of the law of gravity.
He also discovered 3 laws of motion that we call Newton's Laws of Motion.
These laws describe the motion of all objects we experience in our everyday lives.

23. Ch 7, Lesson 4 The Laws of Motion
The 1st Law of Motion
An object at rest tends to stay at rest and an object in motion tends to stay in motion unless acted upon by an unbalanced force.

24. Ch 7, Lesson 4 The Laws of Motion
What does this mean?
Basically, an object will “keep doing what it was doing” unless acted on by an unbalanced force.
If the object was sitting still, it will remain stationary. If it was moving at a constant velocity, it will keep moving.
It takes force to change the motion of an object.

25. Ch 7, Lesson 4 The Laws of Motion
What is meant by unbalanced force?
If the forces on an object are equal and opposite, they are said to be balanced, and the object experiences no change in motion.
If the forces are not equal and opposite, then the forces are unbalanced and the motion of the object changes.

26. Ch 7, Lesson 4 The Laws of Motion
Some examples from real life…
A soccer ball is sitting at rest. It takes an unbalanced force of a kick to change its motion.
Two teams are playing tug of war. They are both exerting equal force on the rope in opposite directions. This balanced force results in no change of motion.

27. Ch 7, Lesson 4 The Laws of Motion
Newton’s First Law is also called the Law of Inertia.
Inertia: the tendency of an object to resist changes in its state of motion.
The First Law states that all objects have inertia. The more mass an object has, the more inertia it has (and the harder it is to change its motion).

28. Ch 7, Lesson 4 The Laws of Motion
More Examples from Real Life
A powerful locomotive begins to pull a long line of boxcars that were sitting at rest. Since the boxcars are so massive, they have a great deal of inertia and it takes a large force to change their motion. Once they are moving, it takes a large force to stop them.
On your way to school, a bug flies into your windshield. Since the bug is so small, it has very little inertia and exerts a very small force on your car (so small that you don’t even feel it).

29. Ch 7, Lesson 4 The Laws of Motion
If objects in motion tend to stay in motion, why don’t moving objects keep moving forever?
Things don’t keep moving forever because there’s almost always an unbalanced force acting upon it.
A book sliding across a table slows down and stops because of the force of friction.
If you throw a ball upwards it will eventually slow down and fall because of the force of gravity.

30. Ch 7, Lesson 4 The Laws of Motion
In outer space, away from gravity and any sources of friction, a rocket ship launched with a certain speed and direction would keep going in that same direction and at that same speed forever.

31. Force equals mass times acceleration.
Newton’s Second Law
Force equals mass times acceleration.
F = ma
Acceleration: a measurement of how quickly an object is changing speed.

32. What does F = ma mean?
Force is directly proportional to mass and acceleration. Imagine a ball of a certain mass moving at a certain acceleration. This ball has a certain force.
Now imagine we make the ball twice as big (double the mass) but keep the acceleration constant. F = ma says that this new ball has twice the force of the old ball.

33. What does F = ma mean?, con’t
Now imagine the original ball moving at twice the original acceleration. F = ma says that the ball will again have twice the force of the ball at the original acceleration.

34. More about F = ma
You double the mass, you double the force. If you double the acceleration, you double the force.
What if you double the mass and the acceleration?
(2m)(2a) = 4F
Doubling the mass and the acceleration quadruples the force.
So what if you decrease the mass by half? How much force would the object have now?

35. What does F = ma say?
F = ma basically means that the force of an object comes from its mass and its acceleration.
Something very massive (high mass) that’s changing speed very slowly (low acceleration), like a glacier, can still have great force.

36. What does F = ma say? con’t
Something very small (low mass) that’s changing speed very quickly (high acceleration), like a bullet, can still have a great force. Something very small changing speed very slowly will have a very weak force.

37. For every action there is an equal and opposite reaction.
Newton’s Third Law
For every action there is an equal and opposite reaction.

38. What does this mean?
For every force acting on an object, there is an equal force acting in the opposite direction.
Right now, gravity is pulling you down in your seat, but Newton’s Third Law says your seat is pushing up against you with equal force. This is why you are not moving.
There is a balanced force acting on you– gravity pulling down, your seat pushing up.

39. Think about it . . .
What happens if you are standing on a skateboard or a slippery floor and push against a wall? You slide in the opposite direction (away from the wall), because you pushed on the wall but the wall pushed back on you with equal and opposite force.
Why does it hurt so much when you stub your toe? When your toe exerts a force on a rock, the rock exerts an equal force back on your toe. The harder you hit your toe against it, the more force the rock exerts back on your toe (and the more your toe hurts).

40. Review
Newton’s First Law: Objects in motion tend to stay in motion and objects at rest tend to stay at rest unless acted upon by an unbalanced force.
Newton’s Second Law: Force equals mass times acceleration (F = ma).
Newton’s Third Law: For every action there is an equal and opposite reaction.

41. Ch 7, Lesson 5 Gravity What is a Force?
FORCE = Any push or pull which causes something to move or change its speed or direction.

42. Ch 7, Lesson 5 Gravity
Gravity: An attraction force between any two objects that have mass.
Newton’s Universal Law of Gravitation: Every object in the universe exerts a gravitational attraction to all other objects in the universe.
The amount of gravitational force depends upon the mass of the objects and the distance between the objects.

43. Acceleration due to gravity =
Ch 7, Lesson 5 Gravity
The greater the mass, the greater the force.
The greater the distance, the less the force.
Acceleration due to gravity =
9.8 m/s/s or 9.8 m/s2

44. Weight is a measure of the gravitational force between two objects.
Ch 7, Lesson 5 Gravity
Weight is a measure of the gravitational force between two objects.
The greater the mass the greater the force (weight).
Measured in units called Newtons (N).

45. Weightlessness – free from the effects of gravity.
Ch 7, Lesson 5 Gravity
Weightlessness – free from the effects of gravity.

46. Gravity and Acceleration
Ch 7, Lesson 5 Gravity
Gravity and Acceleration
Gravity causes all objects to have the same acceleration as they fall.
Another force, air resistance also acts on falling objects.
Air resistance - The force of air exerted on a falling object.
The air pushes up as gravity pulls down.

47. What is Friction? Ch 7, Lesson 5 Gravity
Friction = A force that opposes or slows down motion.
Caused by the physical contact between moving surfaces.
The amount of friction depends upon the kinds of surfaces and the force pressing the surfaces together.
Changes motion into heat.