2 Wednesday, Jan. 27th Agenda Homework Questions/problems/collectBegin section 7.3: Newton’s Laws of MotionNewton’s 1st law, inertia, Newton’s 2nd lawIn-Class assignment:Pg. 236, practice #1-3Movie: “Laws of Motion”Homework: “The Great Plague and Isaac Newton” worksheet
3 HomeworkSection 7.2 reviewPg 233: #1-7Problems/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 callNewton’s Laws of Motion
5 Newton’s 1st LawNewton’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 1st LawYou experience Newton’s 1st 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 unbalancedrearward forces needed tobring you to a stop as thecar stops.
7 InertiaInertia: the tendency of an object to remain at rest or in motion with a constant velocityAll objects have inertia because they resist changes in motion.
8 Newton’s 2nd LawNewton’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 2nd Law a = F m m = F a Just like we did before, we can rearrange the equation F = ma to solve for different things.To solve for acceleration:a = FmTo solve for mass:m = Fa
10 Force = mass X acceleration Newton’s 2nd LawForce = mass X acceleration
11 Force is Measured in Newtons Newton (N): the SI unit of force1 Newton is the force that can give a mass of 1 kg an acceleration of 1 m/s2.1 N = 1 kg X 1 m/s21 N = pounds1 pound = N
12 Newton’s 2nd 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/s2. What is the unbalanced force necessary to produce this acceleration of the lion and the stretcher?Equation: Force = mass X accelerationMass = 175 kgAcceleration = m/s2Solve: Force = 175 kg X m/s2= 115 kg∙m/s2= 115 N
13 Newton’s 2nd 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 = FmForce = 65.0 NMass = kgSolve: a = 65.0 N = 448 m/s20.145 kg
14 Newton’s 2nd 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/s2, what is the shark’s mass?Equation: m = FaForce = 25,000 NAcceleration: m/s2Solve: m = 25,000 N = 20,000 kg1.25 m/s2