1. Pre Assessment Discussion
Roller Coasters
Pre Assessment Discussion

2. Table 1 t seconds (s) x, y, h, d meters (m) F Newtons (N) v
Measurement
Variable
Unit
Time t
seconds (s)
Displacement
x, y, h, d
meters (m)
Force F
Newtons (N)
Velocity v
meters/second (m/s)
Acceleration a
meters/second2 (m/s2)
Momentum p
kg (m/s)
Potential Energy
P or PE
Joules (J)
Kinetic Energy
K or KE
Mass m
kilograms (kg)
Height h
Acceleration due to gravity g
10 m/s2

3. 1. How do you describe (or define) potential energy?
An object’s gravitational potential energy (is directly proportional to) depends upon its weight (mg where m is the object’s mass and g is the acceleration due to gravity) and height (h) above a reference surface (PE = mgh).

4. Example
How much potential energy is there in a 5-kg object which is 23 m above the ground?
P = mgh
P = (5 kg) (10 m/s2) (23 m)
P = 1150 J

5. 2. How do you describe (define) kinetic energy?
An object’s kinetic energy (is directly proportional to) depends on its mass and the speed squared (KE = ½ mv2)

6. Example
What is the kinetic energy of a kg marble that has a velocity of 2.01 m/s?
K = ½ m v2
K = ½ ( kg) (2.01 m/s)2
K = ½ ( kg) (4.04 m2/s2)
K = J How many sig figs?
K = J or 6.87 x 10-3 J

7. 3. When is potential energy the greatest in this situation?
For the bouncing basketball at the highest point of its bounce above the ground, the energy of the ball is a maximum potential energy (no kinetic energy).

8. 4. When is potential energy the least in this situation?
Gravitational potential energy is least when the ball is closest to ground level.
P = mgh
m and g do not change but the h becomes less

9. 5. When is the kinetic energy the least in this situation?
When the ball is not in motion or at the highest point in its bounce where it actually stops moving for an instant
K = ½ m v2
m does not change but if v gets bigger so does K.

10. 6. When is the kinetic energy the greatest in this situation?
Just before and just after bouncing, the kinetic energy of the ball is greatest.
K = ½ mv2
m does not change but as v increases so does K

11. 7. If the basketball is dropped or bounced from a greater height, how does the ball’s potential (kinetic) energy compare to the original situation?
Since the original height is greater than in the original situation, the potential of the basketball will be greater. And the kinetic energy of the ball will be greater than in the original situation because it falls from a greater height. Its speed will be greater just before it hits the ground (ignoring the effects of air resistance).

12. Velocity Example
What is the velocity of an object that was displaced 4 m in 10 seconds?
V = displacement / time
V = d/t
V = 4 m / 10 s
V = 0.4 m/s

13. Acceleration Example
What is the acceleration of an object that slowed from 16 m/s to 10 m/s in 3 seconds?
A = change in velocity / time
A = final velocity – initial velocity / time
A = (10 m/s – 16 m/s) / 3 s
A = -6 m/s / 3 s
A = - 2 m/s2

14. Force Example
What is the force of a 10-kg object with an acceleration of 3 m/s?
F = mass x acceleration
F = m a
F = (10 kg) (3 m/s2)
F = 30 Newtons or 30 N

15. Roller Coaster Discussion
After viewing the video, discuss the following questions.

16. What do you know about the energy at various points in these rides?

17. What other systems of moving objects are similar to roller coasters
What other systems of moving objects are similar to roller coasters? How are they different?
(Possible examples include toy cars and tracks, professional rollerblade, skateboard tracks, professional motorcycle or automobile racetracks)

18. What do you think about how safe roller coaster rides are for people?

19. What working roller coaster designs are the safest for people?

20. Evaluation of this unit
There are three main parts to the evaluation process.

21. Part 1
Design and build a roller coaster to determine how a marble’s potential energy is affected by changing its height and mass.

22. Part 2
Make and record all key measurements and score the final working energy coaster design of your peers and your own.

23. Part 3
Complete an energy-coaster written report for the final working design. Write your answer to the questions regarding the energy-coaster.
Questions and Rubric (how it is graded) will be handed out to you.