Newton’s Third Law + Review Newton’s Third Law Examples Review Quiz Outline

Action  Reaction Newton’s 3rd Law NIII definition Newton’s 3rd Law “If object A exerts a force on object B, then object B exerts a force equal in magnitude and opposite in direction on A” Action  Reaction

The Math FA on B = - FB on A B Fapp A

Example: Two blocks are pushed with an applied force Example: Two blocks are pushed with an applied force. Determine the acceleration of the blocs and the action/reaction forces FAB and FBA. B A Fapp

Review

Draw the v-t and a-t graphs for the x-t graph Walk–Back/Forth Draw the v-t and a-t graphs for the x-t graph x [m] t [s]

Exercise Ax = __________ Bx = __________ Ay = __________ QQ29: 2-D Components Exercise Determine the numerical values of the x and y components of each vector: y y 120 5 x x 45 10 Ax = __________ Ay = __________ Bx = __________ By = __________ What would A+B look like ?

We divide the contact force into two components” normal force : is perpendicular to the surfaces in contact friction : is parallel to the surface

Demo Ex: Two blocks are connected over a frictionless pulley. What is the acceleration of the system given no friction. m1=2kg m2=1kg

Demo Ex: A block is moving down a ramp that makes an angle θ with the horizontal. What is the acceleration of the system given that there is friction. m1 θ

QQ38: Inequality Example: A horizontal force of 150 N is applied to a 50 kg box on a level floor. The coefficient of static friction between the box and the floor is 0.5. What magnitude of the frictional force on the box.

What to review look over all the lecture notes write down ‘key concepts’ that you think are important be able to use x-t, v-t, a-t graphs understand normal forces (ramps, level) be able to find acceleration for simple systems free body diagrams look over projectile motion don’t worry about any long derivations we did in class!