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Wednesday, Jan. 27 th Agenda Homework Questions/problems/collect Begin section 7.3: Newton’s Laws of Motion –Newton’s 1 st law, inertia, Newton’s 2 nd.

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Presentation on theme: "Wednesday, Jan. 27 th Agenda Homework Questions/problems/collect Begin section 7.3: Newton’s Laws of Motion –Newton’s 1 st law, inertia, Newton’s 2 nd."— Presentation transcript:

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2 Wednesday, Jan. 27 th Agenda Homework Questions/problems/collect Begin section 7.3: Newton’s Laws of Motion –Newton’s 1 st law, inertia, Newton’s 2 nd law In-Class assignment: –Pg. 236, practice #1-3 Movie: “Laws of Motion” Homework: “The Great Plague and Isaac Newton” worksheet

3 Homework  Section 7.2 review Pg 233: #1-7  Problems/Questions?  Turn In

4 Section 7.3: Newton’s Laws of Motion  Every motion you see or experience is related to a force.  Sir Isaac Newton described the relationship between motion and force in 3 laws that we now call Newton’s Laws of Motion

5 Newton’s 1 st Law  Newton’s First Law: An object at rest remains at rest and an object in motion maintains its velocity unless it experiences an unbalanced force.

6 Newton’s 1 st Law  You experience Newton’s 1 st law when you ride in a car.  As the car comes to a stop, you can feel your body continue to move forward.  Your seat belt and the friction between your pants and the seat stop your forward motion.  They provide the unbalanced rearward forces needed to bring you to a stop as the car stops.

7 Inertia  Inertia: the tendency of an object to remain at rest or in motion with a constant velocity  All objects have inertia because they resist changes in motion.

8 Newton’s 2 nd Law  Newton’s Second Law: The unbalanced force acting on an object equals the object’s mass times its acceleration.  Force = (mass) X (acceleration) F = ma

9 Newton’s 2 nd Law  Just like we did before, we can rearrange the equation F = ma to solve for different things.  To solve for acceleration: a = F m  To solve for mass: m = F a

10 Newton’s 2 nd Law Force = mass X acceleration

11 Force is Measured in Newtons  Newton (N): the SI unit of force  1 Newton is the force that can give a mass of 1 kg an acceleration of 1 m/s 2.  1 N = 1 kg X 1 m/s 2  1 N = pounds  1 pound = N

12 Newton’s 2 nd law example, pg 236 Zookeepers lift a stretcher that holds a sedated lion. The total mass of the lion and stretcher is 175 kg, and the lion’s upward acceleration is m/s 2. What is the unbalanced force necessary to produce this acceleration of the lion and the stretcher? Equation: Force = mass X acceleration Mass = 175 kg Acceleration = m/s 2 Solve: Force = 175 kg X m/s 2 = 115 kg∙m/s 2 = 115 N

13 Newton’s 2 nd law example #2 Assume that a catcher in a professional baseball game exerts a force of 65.0 N to stop a ball. If the baseball has a mass of kg, what is its acceleration as it is being caught? Equation: a = F m Force = 65.0 N Mass = kg Solve: a = 65.0 N = 448 m/s kg

14 Newton’s 2 nd law example #3 A whale shark is being lifted by a crane for transport to an aquarium. The crane uses a force of 25,000 N to lift the shark. If the shark’s acceleration is 1.25 m/s 2, what is the shark’s mass? Equation: m = F a Force = 25,000 N Acceleration: 1.25 m/s 2 Solve: m = 25,000 N = 20,000 kg 1.25 m/s 2

15 In-Class Assignment  Practice problems, pg. 236, # 1-3

16 Movie “Laws of Motion”

17 Homework  Worksheet: “The Great Plague and Isaac Newton”


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