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Tsokos lesson 2-4 newton’s first law

IB Assessment Statements Topic 2.2, Forces and Dynamics 2.2.4. State Newton’s first law of motion. 2.2.5. Describe examples of Newton’s first law. 2.2.6. State the condition for translational equilibrium. 2.2.7. Solve problems involving translational equilibrium.

Objectives Relate situations in which the acceleration is zero, to equilibrium situations in which the net force is zero Find the net force on a body using the methods of vector addition Solve problems of equilibrium

Introductory Video

Newton’s First Law When no forces act on a body, that body will either remain at rest or continue to move along a straight line with constant speed.

Newton’s First Law When no forces act on a body, that body will either remain at rest or continue to move along a straight line with constant speed. What happens when a force acts on a body or when existing forces become unbalanced?

Newton’s First Law When no forces act on a body, that body will either remain at rest or continue to move along a straight line with constant speed. What happens when a force acts on a body or when existing forces become unbalanced? Acceleration

Newton’s First Law When no forces act on a body, that body will either remain at rest or continue to move along a straight line with constant speed. What happens when a force acts on a body or when existing forces become unbalanced? Acceleration Acceleration in what form?

Newton’s First Law When no forces act on a body, that body will either remain at rest or continue to move along a straight line with constant speed. What happens when a force acts on a body or when existing forces become unbalanced? Acceleration Acceleration in what form? Change in velocity Change in direction

Newton’s First Law Also called the Law of Inertia Reluctance of a body to change its state of motion

Inertial Frames of Reference A system on which no forces act (inert) Observers in all reference frames should come up with the same answers Are you an inertial reference frame?

Inertial Frames of Reference A system on which no forces act Observers in all reference frames should come up with the same answers Are you an inertial reference frame? With the rotation of the earth, you have a tangential speed of 464 m/s

Inertial Frames of Reference A system on which no forces act Observers in all reference frames should come up with the same answers Are you an inertial reference frame? With the rotation of the earth, you have a tangential speed of 464 m/s With the orbit of the earth around the sun, we have a tangential speed of 3x104 m/s

Inertial Frames of Reference A system on which no forces act Observers in all reference frames should come up with the same answers Are you an inertial reference frame? With the rotation of the earth, you have a tangential speed of 464 m/s With the orbit of the earth around the sun, we have a tangential speed of 3x104 m/s However, because of the radii involved, the acceleration over short periods of time is minimal

Equilibrium Net force on a body is zero Neutral equilibrium – after a displacement, the sum of the forces acting on the body are still zero Stable equilibrium – after a displacement, the sum of the forces acting on the body tends to move the body back to its initial position Unstable equilibrium – after a displacement, the sum of the forces acting on the body tend to accelerate the body away from its initial position Sum of the forces is key!

Objectives Relate situations in which the acceleration is zero, to equilibrium situations in which the net force is zero Find the net force on a body using the methods of vector addition Solve problems of equilibrium

IB Assessment Statements Topic 2.2, Forces and Dynamics 2.2.4. State Newton’s first law of motion. 2.2.5. Describe examples of Newton’s first law. 2.2.6. State the condition for translational equilibrium. 2.2.7. Solve problems involving translational equilibrium.

Questions?

Homework #1-15