1. 8.1 Energy & Motion Key Questions
How Are Energy, Work, and Power Related?
What Are the Two Types of Energy?
p. 290: Advantages/disadvantages of using wind technology?

2. Energy The ability to do work or cause change.
Work is done when force (which is a push or a pull) moves an object.

3. When you work on something, some energy is transferred to the object.
The Metric (SI) unit for energy is
Joule
(this unit is also used for “work”).
nWhen

4. Power or energy is transferred,
is the rate at which work is done
or energy is transferred,
or the amount of energy transferred in a unit of time.
The transfer of energy is work.
When energy is transferred, the object upon which the work is done, gains energy.
So power, work, and energy are related.

5. Power= Energy Transferred Time
What is the equation that shows the relationship between Work, Power, and Energy?
Power= Energy Transferred Time

6. Snow shovel or snowblower p. 291?
Since Power =
Energy Transferred / time
The Snowblower has MORE POWER since it transfers the same amount of energy but in LESS TIME!
Elevator or stairs to lift a box to 10th floor?
Elevator has more power since it can move box faster.
Each transfers the same amount of energy when it moves the snow the same distance.
However, which one moves the snow faster?

7. What Are Two Types of Energy?

8. Kinetic Energy The energy an object has due to its motion.
(energy of motion)

9. object’s mass and object’s velocity (speed)
The factors of kinetic energy are ____________and ___________.

10. Do the factors – mass and speed really matter?
Does Mass Matter?
Tennis ball is rolled on floor and hits your little toe. Does it really hurt that much?
Now what if we roll a bowling ball at same speed at your toe?
YIKES! Watch out!
Which has more kinetic energy?
Tennis ball lobbed at you?
Or a Tennis ball thrown at 90 mph by a professional pitcher?
So Speed Matters!

11. OR What is the formula for kinetic energy?
Both are going 5 m/s. Which has greater KE, the real car or the toy car?
The Real Car:
Because of its
Greater Mass

12. Kinetic energy increases as __________ increases.3 1
Kinetic energy increases as __________ increases. 2
MASS

13. Calculating Kinetic Energy
Girl and dog are running 2 m/s. Dog has mass of 20 kg
Girl has mass of 60 kg.
Dog = 1/2 x 20 kg x (2 m/s)2
= kg x 4m2/s2
= Joule
Girl = ½ x 60 kg x (2 m/s)2
= x 4m2/S2
= Joules
KE = 1 x Mass x Speed2 2 Note: 1 kg x M2 = I joule S2 If the dog speeds up and runs at 4 m/s. What would be it’s new KE? Dog = 1/2 x 20 kg x (4 m/s)2 = 10 kg x 16m2/s2 = 160 Joule

14. Remember from last example: When Dog was going 2 m/s = 40 Joules
p. 293 What has greater effect on an object’s kinetic energy? Doubling it’s mass or doubling it’s speed?
Remember from last example:
When Dog was going 2 m/s = 40 Joules
When Dog sped up to 4 m/s = 160 Joules
So, doubling speed has a greater effect on the kinetic energy because as you see from equation, speed is squared.
KE = 1 x Mass x Speed2 2

15. Does an object have to be moving in order to have energy?
NO! Some objects have energy as a result of their position or shape.
By position:
If you lift a book up to your head from the floor you transfer energy to it.
The energy you transferred is stored or “held in readiness”.
By Shape:
The same is true when you compress a spring. It now has “potential” to do work.

16. Energy that results from the position or shape of an object.
Potential Energy
Energy that results from the position or shape of an object.
This type of energy
has the
POTENTIAL
to do
work

17. Gravitational Potential Energy (GPE)
The energy associated with an object’s height. Who has more GPE – the boy or girl? The girl!

18. Gravitational Potential Energy
The energy associated with an object’s height.

20. I do ! I do! Which rock climber has the greatest potential energy?
Gravitational Potential Energy
The rock climbers have gravitational potential energy, which is potential energy related to an object's height.
Which rock climber has the greatest potential energy?
Red Shirt guy:
600 N x 4 m=
2,400 J
The force you use to lift the object is equal to it’s weight and is expressed in Newtons. The distance you move the object is it’s height above the ground

21. What is the unit of measurement for force?
Newton
What is the unit of measurement for force?

22. Which plant has more potential gravitational energy?

23. Elastic Potential Energy
The energy associated with objects that can be compressed or stretched.
When does the trampoline have the greatest elastic potential energy?
When it is stretched the most! 1 3 2

24. GPE Problem (weight known)
John’s little brother Jim annoyed John. Jim weighs 100 N. John tied his brother in a tree
10 m off the ground.
What is his little brother’s GPE?

25. Hey Ferb, I know what we’re gonna do today
Hey Ferb, I know what we’re gonna do today. Let’s calculate Candace’s kinetic energy if she has a mass of 100kg and is running at 3m/s to get mom to bust us.

26. What Are the Two Types of Energy?
The two types of energy are and .
Kinetic energy
potential energy

27. Question 1 4.1 Energy is the ability to do work or cause __________.
Section Check
4.1
Question 1
Energy is the ability to do work or cause __________.
A. change
B. heat
C. motion
D. work

28. Section Check
4.1
Answer
The answer is A. Energy is the ability to do work or to cause change (and has several different forms).

29. Question 2 4.1 The kinetic energy of an object depends on __________.
Section Check
4.1
Question 2
The kinetic energy of an object depends on __________.
A. the object’s mass and speed
B. the object’s mass
C. the object’s speed
D. the acceleration of the object

30. Section Check
4.1
Answer
 The answer is A. Kinetic energy depends on both the mass and speed of the moving object.

31. Video Resources Potential vs Kinetic