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.

Adding force vectors

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

Weight, normal force and a box

Unwanted weight loss(descending)

Pulling a box Note: FN is less than mg

Box sliding down

Getting the car out of the mud

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

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

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?

Where does the thread break?