Newton’s 2 nd Law: More Practice. Newton’s 3 rd Law: Student Learning Goals The student will be able to state Newton’s 3 rd Law and apply it in qualitative.

Newton’s 2Newton’s 2ndnd Law: Law:More PracticeMore Practice



Newton’s 3Newton’s 3rdrd Law: Law: Student Learning GoalsStudent Learning Goals

The student will be able to state The student will be able to state Newton’s 3Newton’s 3rdrd Law and apply it in Law and apply it in qualitative and quantitative terms to qualitative and quantitative terms to explain the effect of forces acting on explain the effect of forces acting on objects. (B3.4)objects. (B3.4)

Newton’s 3Newton’s 3rdrd Law LawSPH4CSPH4C

Newton’s 3Newton’s 3rdrd Law of Law of MotionMotion

““For every action, there is an equal For every action, there is an equal and opposite reaction.”and opposite reaction.”


““For every action, there is an equal For every action, there is an equal and opposite reaction.”and opposite reaction.”

More accurately: for every action More accurately: for every action force on object B due to object A, force on object B due to object A, there is a reaction force, equal in there is a reaction force, equal in magnitude but opposite in direction, magnitude but opposite in direction, on object A due to object B.on object A due to object B.


What does this mean in practice? What does this mean in practice? Examples:Examples:

An object near the Earth’s surface An object near the Earth’s surface experiences a gravitational force of 15 experiences a gravitational force of 15 N [down]. What is the reaction force?N [down]. What is the reaction force?




The Earth experiences a gravitational The Earth experiences a gravitational force of 15 N [up].force of 15 N [up].





The same object resting on a table The same object resting on a table experiences a normal force of 15 N experiences a normal force of 15 N [up]. What is the reaction force?[up]. What is the reaction force?


What does this mean in practice? Examples:What does this mean in practice? Examples: An object near the Earth’s surface An object near the Earth’s surface

experiences a gravitational force of 15 N experiences a gravitational force of 15 N [down]. What is the reaction force?[down]. What is the reaction force?


The same object resting on a table The same object resting on a table experiences a normal force of 15 N [up]. experiences a normal force of 15 N [up]. What is the reaction force?What is the reaction force?

The 15 N [down] normal force on the The 15 N [down] normal force on the table.table.

Newton’s 3Newton’s 3rdrd Law in Law in PracticePractice

A 55 kg person standing on a A 55 kg person standing on a frictionless ice rink throws a 5.0 kg frictionless ice rink throws a 5.0 kg ball with a force of 25 N [E]. What is ball with a force of 25 N [E]. What is the acceleration of the: (a) ball; (b) the acceleration of the: (a) ball; (b) person?person?



The acceleration of the ball is:The acceleration of the ball is: ][0.50.5

][252 E

kg

EN

m

Fa

smnet



The acceleration of the person is:The acceleration of the person is:][45.055

][252 W

kg

WN

m

Fa

smnet

More PracticeMore Practice

Hands On with Newton’s 3Hands On with Newton’s 3rdrd Law Law

Newton’s 2 nd Law: More Practice. Newton’s 3 rd Law: Student Learning Goals The student will be able to state Newton’s 3 rd Law and apply it in qualitative.

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