1. Classical Mechanics Midterm 2 Review Force and Energy
Midterm this Friday March 13
Classical Mechanics Midterm 2 Review Force and Energy
Newton’s Laws of Motion
Forces and Free Body Diagrams
Friction
Work and Kinetic Energy
Conservative Forces and Potential Energy
Work and Potential Energy
Knowledge of Units 1-3 will be useful
“Playing with Blocks”

2. Midterm Exam Multiple choice…but show your work and justification.
Calculations
Forces and Free-Body Diagrams
Weight and Pulleys
Springs
Friction
Gravitational
Normal
Work Calculations
Conservation of Energy
Conceptual questions…like checkpoint problems.
Bring calculators and up to five sheets of notes

3. Midterm Exam 2 Sample exam
Folder under Files menu on PHYS1500 Canvas Website
Phys 1500 Exams
- Spring 2013:
- Solutions:
- Long Sample:
- Long Solutions:
Phys 2210 Exams
- Practice :
- Spring 2015:

4. Force and Energy Summary

5. (otherwise objects velocity is constant)
Determining Motion
Force
Energy
Unbalanced Forces  acceleration
(otherwise objects velocity is constant)
Total Energy  Motion, Location
Determine Net Force acting on object
Work
Motion from Energy conservation
Use kinematic equations to determine resulting motion

6. Unit 4: Newton’s Laws

7. Unit 5: Forces and Free-Body Diagrams
Box

8. Inventory of Forces Weight Normal Force Tension Gravitational Springs
…Friction

10. Force Summary

11. Unit 6: Friction

12. Friction

13. Unit 7: Work and Kinetic Energy

14. Work-Kinetic Energy Theorem
The work done by force F as it acts on an object that moves between positions r1 and r2 is equal to the change in the object’s kinetic energy:
But again…!!!

15. The Dot Product

16. Vectors!!!

17. Unit 8: Conservative Forces & Potential Energy

18. Unit 8: Conservative Forces & Potential Energy

19. Unit 9:Work and Potential Energy

20. Energy Conservation Problems in general
For systems with only conservative forces acting
Emechanical is a constant

21. Gravitational Potential Problems
conservation of mechanical energy can be used to “easily” solve problems.
Define coordinates: where is U=0?
Add potential energy from each source. as

22. Example Problem : Block and spring
A 2.5 kg box is held released from rest 1.5 m above the ground and slides down a frictionless ramp. It slides across a floor that is frictionless, except for a small section 0.5 m wide that has a coefficient of kinetic friction of 0.2. At the left end, is a spring with spring constant 250 N/m. The box compresses the spring, and is accelerated back to the right.
  What is the speed of the box at the bottom of the ramp?
What is the maximum distance the spring is compressed by the box?
Draw a free-body diagram for the box while at the top of the incline ? When the spring is maximally compressed? When the box is sliding on the rough spot to the right?
What is the total work done by friction? Each way?
What height does the box reach up the ramp after hitting the spring once?
Where will the box come to rest?
2.5 kg
h=1.5 m
d = 0.50 m
mk = 0.4
k=250 N/m

23. Example Problem: Free-Body Diagram
1) FBD N T m2 g f T m1 m1
m2g
m1g

24. Example Problem: Free-Body Diagram
1) FBD
2) SF=ma N T m2 g f T m1 m1
m2g
N = m2g
m1g
T – m m2g = m2a
m1g – T = m1a
add
m1g – m m2g = m1a + m2a
m1g – m m2g
a =
m1 + m2

25. Example Problem: Free-Body Diagram
1) FBD
2) SF=ma N T m2 g f T m1 m1
m2g
m1g
m1g – T = m1a
m1g – m m2g
T = m1g – m1a
a =
m1 + m2
T is smaller when a is bigger

26. Example Problems

27. Example Problem

28. Block

29. Pushing Blocks

30. Example Problems

31. Example: Pendulum h h
Conserve Energy from initial to final position.

32. Example Problems

33. Example: Pulley and Two Masses
A block of mass m1 = 1 kg sits atop an inclined plane of angle θ = 20o with coefficient of kinetic friction 0.2 and is connected to mass m2 = 3 kg through a string that goes over a massless frictionless pulley. The system starts at rest and mass m2 falls through a height H = 2 m.
  Use energy methods to find the velocity of mass m2 just before it hits the ground?
H = m H
m2 = 2  kg m1 θ m2

34. Example Problems

35. Example Problems

36. Force and Energy Summary