Chapter 4 AP Physics BMotion and Force: Dynamics

•Dynamics is the study of force and its effect of motion.•A force is a push or pull that can change the inertia of an object.

Newton’s First Law of Motion

• Every body continues in its state of rest or motion, unless acted upon by a force.• This is often called the law of inertia.• Inertia is a tendency of an object to

maintain its state of motion.• Reference frames where Newton’s 1st law

of motion hold are called inertial reference frames.

Newton’s Second Law of Motion

• F=ma• The acceleration of an object is directly

proportional to the net force acing on it and is inversely proportional to its mass. The direction of the net force is the direction of motion.

• a= Fnet /m

Mass

• Mass can be defined as the quantity of matter.• Mass can also be defined as a

measure of inertia.• The SI base unit of mass is the kg.

Example Problems

• See Example 4-1• See Example 4-2

Newton’s Third Law of Motion

• Whenever one object exerts a force on a second object, the second object exerts an equal and opposite force on the first.

• m1 a1 = m2 a2

• See Conceptual Example 4-3

• See subscript usage on page 85.

• F gp and Fpg

Homework p 103-104

•Questions 2-5•Problems 1-6, 7-11•Due Monday BOP