18.1 The Origins of the Reformation

10-3/10-4: Newtons Laws of MotionWhat are Newtons threelaws of motion?

1Anticipatory Set

California StandardsScience Standard 8.2.e: Students know that when the forces on an object are unbalanced, the object will change its velocity.Science Standard 8.2.f: Students know the greater the mass of an object, the more force is needed to achieve the same rate of change in motion.

3Inputinertia: the tendency of an object to resist a change in motion.momentum: a characteristic of a moving object that depends on both the mass and the velocity of the object.law of conservation of momentum: in the absence of outside forces, the total momentum of objects that interact does not change.

4Input & Modeling

Newtons First Law of MotionAn object will remain at rest or moving at a constant velocity unless it is acted upon by an unbalanced force.Inertia is the tendency of an object to resist change in motion.Another name for Newtons First Law of Motion is the Law of Inertia.The greater the objects mass, the greater its inertia.

5Input & Modeling

Newtons First Law of Motion

6Input & Modeling

Newtons First Law of Motion

7Input & Modeling

Newtons Second Law of MotionAcceleration depends on the net force acting on the object and on the objects mass.Acceleration = Net Force MassAcceleration is measured in meters per second per second (m/s/s).Net force is measured in Newtons (N), and mass is measured in kilograms (kg).Net Force = Mass x Acceleration

8Input & Modeling

Newtons Second Law of Motion

9Input & Modeling

A speedboat pulls a 55-kg water-skier. The skier accelerates at 2.0 m/s2. Calculate the net force that causes this acceleration.a = Fnet/m or Fnet = m x a

Fnet = m x a F = 55 kg x 2.0 m/s2F = 110 kg m/s2F = 110 N

10C4U

Practice Problem

What is the net force on a 1,000-kg object accelerating at 3 m/s2?(1,000 kg x 3 m/s2)3,000 N

11C4U

Practice Problem

What net force is needed to accelerate a 25-kg cart at 14 m/s2?(25 kg x 14 m/s2)350 N

12Input & Modeling

Newtons Third Law of MotionNewtons third law of motion states that if one object exerts a force on another object, then the second object exerts a force of equal strength in the opposite direction on the first object.Momentum = Mass x VelocityThe unit for momentum is measured in kilogram-meters per second (kgm/s)

13Input & Modeling

Newtons Third Law of Motion

14Input & Modeling

Which has more momentum: a 3.0-kg sledgehammer swung at 1.5 m/s or a 4.0-kg sledgehammer swung at 0.9 m/s?Momentum = Mass x Velocity

Smaller sledgehammer = 3.0 km x 1.5 m/s = 4.5 kgm/sLarger sledgehammer = 4.0 km x 0.9 m/s = 3.6 kgm/s

15C4U

Practice Problem

A golf ball travels at 16 m/s, while a baseball moves at 7 m/s. The mass of the golf ball is 0.045 kg and the mass of the baseball is 0.14 kg. Which has greater momentum?Golf ball: 0.045 kg x 16 m/s = 0.72 kgm/sBaseball: 0.14 kg x 7 m/s = 0.98 kgm/sThe baseball has greater momentum.

16C4U

Practice Problem

What is the momentum of a bird with a mass of 0.018 kg flying at 15 m/s?momentum = 0.018 kg x 15 m/s momentum = 0.27 kgm/s

17Input & Modeling

Law of Conservation of MomentumThe total momentum of any group of objects remains the same, or is conserved, unless outside forces act on the objects.Friction is an example of an outside force.

18Input & Modeling

Conservation of Momentum

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Conservation of MomentumIn the absence of friction, momentum is conserved when two train cars collide.

20 HOMEWORK CONNECTION

Read pages 389-399 in your Science textbook.

Create a colored comic or poster that illustrates all three of Newtons Laws of Motion.

Write a detailed SUMMARY of the section and complete the UNANSWERED QUESTIONS section of your notes.

Choose two of the remaining Depth & Complexity ICONS in your notes and explain how they relate to this section.

Here Comes ScienceThey Might Be GiantsJohn Linnell/John FlansburghHere Comes Science2009iTunes 10.0.1, QuickTime 7.6.6