1. Chapter 4: Dynamics, Newton’s Laws
First Law: Every body stays in its state of motion( rest or uniform speed) unless acted on by a non zero net force.
Second Law: The acceleration is directly proportional to the net force and inversely proportional to the mass:
Third Law: Action is equal to reaction.

4. Adding force vectors

5. pulling a sled, Michelangelo’s assistant
For forward motion: FAG> FAS FSA > FSG

7. Weight, normal force and a box

9. Unwanted weight loss(descending)

12. Pulling a box
Note: FN is less than mg

14. Box sliding down

16. Getting the car out of the mud

18. Atwood’s Machine FT=? a=?
Draw a free body diagram for each mass and choose up positive, then a2= a , a1= -a
FT - m1g = m1a1= -m1a
FT – m2g = m2a2= m2a
(m1–m2)g=(m1+m2)a

20. = mass of elevator and load
Work our the acceleration of the system shown if it is pulled up with a force of 200N.

21. Why does the force need to pull the backpack up increase?
Precautions in Yosemite Park
Why does the force need to pull the backpack up increase?

22. Where does the thread break?