1. Instructor: Dr. Tatiana Erukhimova
Physics 218: Mechanics
Instructor: Dr. Tatiana Erukhimova
Lecture 9

2. Quiz (hw Ch 6)
A block of mass m starts at rest at the point x=A, y=B. At time t=0 two forces begin to act on it:
Here c1, c2, b1 and b2 are known constants. Where will the block be at any subsequent time, t?

3. Force of tension
Massless, unstretchable string; frictionless pulley

5. Block 1, of mass m1, is placed at rest on an inclined plane
Block 1, of mass m1, is placed at rest on an inclined plane. It is attached by a massless, unstretchable string to block 2, of mass m2. The pulley is massless and frictionless and just changes the direction of the tension in the string. The coefficient of friction between the plane and m1 is the constant . 1 2
Determine what range of values for mass m2 will keep the system at rest.
Find acceleration if mass 2 goes down.

6. Friction everywhere. 2 F 1
Find F necessary to drag the box 1 at constant speed.

7. 105 Heldenfels First exam Tuesday, September 28
Section 807 and half of 808 start at 7 pm
Section 809 and half of 808 start at 8:05 pm

8. No calculators and cell phones
BRING YOUR STUDENT ID!
No calculators and cell phones
All liquids, gels and aerosols must be in three-ounce or smaller containers.

9. What is included?
Chapters 1-6
Kinematics, vectors, Newton’s Laws

10. Kinematics

11. In components:

12. If is given, you can find and

13. Vectors

14. Newton’s 2nd Law

15. Newton’s 3rd Law N N

16. Friendly advice
DO NOT…

17. DO NOT use Const acceleration case formulas when acceleration is a function of time. You have to integrate or differentiate! What are the Const acceleration case formulas?

18. DO NOT write the vector sign over a projection!

19. DO NOT forget that Fp has two components: Fpcos θ and Fpsin θQ

20. Do Not Forget to
Write down what is given and express the answer in terms of what is given
Box the answer
Indicate the origin and positive x and y

21. Have a great day!
Good luck!