# Newton’s 2 nd and 3 rd laws Wednesday, October 1, 2014.

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Newton’s 2 nd and 3 rd laws Wednesday, October 1, 2014

Wednesday, 10/1 Unit 3: Work and Forces  If you are new to the class please come see me.  New seating chart for 2SW  Take out your warm-up and in class problems from Monday.  Read the ‘I can’ statements on the side board.  Review dates below  Upcoming dates  Wednesday, 10/1 – quiz  Tuesday, 10/7 - quiz  Thursday, 10/9 – Unit 3 test  Friday, 10/24 – last day to turn in 2SW extra credit  Friday, 10/31 – end of 2SW

Warm-up For each object listed in the table, find the weight of the object (on Earth) in Newtons G:G:G: U:U:U: E:E:E: S:S:S: MassWeight 25 kg 1.5 kg 115 kg

Newton’s 2 nd Law – Practice problem 1 A car has a mass of 550 kg. 1. Find the weight of the car on Earth 2. Find the net force needed to accelerate the car at 12 m/s 2. 3. If a net force of 2200 N were to act on the car, what would its acceleration be?

Newton’s 2 nd Law – Practice problem 2 A sled weighs 2500 N on Earth 1. What is the mass of the sled? 2. What is the mass of the sled on the moon, where g = 1.6 m/s 2 ? 3. What is the weight of the sled on the moon? 4. What net force is needed to accelerate the object at 4.0 m/s 2 on the moon?

Review in class problems

Balloon Demo

Summarize Newton’s 3 rd Law of Motion

Newton’s 3 rd Law, the Law of Interaction If (object 1) exerts a (type) force in the (direction) direction on (object 2), then (object 2) is exerting a (same type) force directed (opposite direction) on (object 1) simultaneously.

Source: http://www.physicsclassroom.com/class/newtlaws/Lesson-4/Newton-s-Third-Law

http://www.physicsclassroom.com/class/newtlaws/Lesson-4/Newton-s-Third-Law

Quiz  Put your phone in your bag. If you don’t have a bag put your phone on my desk  When you are done flip your quiz over.

Law of Universal Gravitation

Video  http://dsc.discovery.com/videos/assignment- discovery-shorts-newtons-explanation-of- gravity.html http://dsc.discovery.com/videos/assignment- discovery-shorts-newtons-explanation-of- gravity.html

Take LUG notes

Practice Problem 1 Tom has a mass of 70.0-kg and Sally has a mass of 50.0-kg. Tom and Sally are standing 20.0m apart on the dance floor. Sally looks up and sees Tom. She feels an attraction. If the attraction is gravitational, find its size. Assume that both Tom and Sally can be replaced by spherical masses.

Practice Problem 2  What is the gravitational attraction between two spheres ( m sphere = 1.67 X 10 -27 kg) at a distance of 5.0 X 10 -15 m?  7.44 x10 -36 N

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