Advanced Physics

Chapter 4Motion and Force: Dynamics

Chapter 4

4-1 Force 4-2 Newton’s First Law of Motion 4-3 Mass 4-4 Newton’s Second Law of Motion 4-5 Newton’s Third Law of Motion 4-6 Weight-the Force of Gravity and the

Normal Force 4-7 Solving Problems with Newton’s Laws 4-8 Applications Involving Friction and Inclines 4-9 Problem Solving

4-1 Force

Force• a push or a pull

4-2 Newton’s First Law of Motion

Newton’s First Law of Motion

Net Force• Vector sum of all

forces acting on an object

Inertia• Tendency of a body to

maintain its state of motion

4-2 Newton’s First Law of Motion

Inertial vs. non-inertial reference frames

a

4-3 Mass

Mass vs. Weight

4-4 Newton’s Second Law of Motion

Newton’s Second Law of Motion Force

• An action capable of accelerating an object (N)

equation:

F = ma

4-5 Newton’s Third Law of Motion

Newton’s Third Law of Motion

4-5 Newton’s Third Law of Motion

Net Force Action-Reaction

Force

4-6 Weight-Force of Gravity and Normal Force

Weight (Fg)• Force of gravity on an

object Contact Force Normal Force (Fn)

• Contact force that acts perpendicular to the surface of contact

Are Fg and Fn action-reaction forces?

Does anyone remember the five forces equation?

(4-7)

4-7 Solving Problems with Newton’s Laws

Free-Body (force) diagram• Five forces

Tension• The force exerted

when a flexible cord pulls on an object

4-7 Solving Problems with Newton’s Laws

Problem solving: If 150 N of

upward force is applied to a 35 kg object calculate its rate of acceleration

150 N

4-8 Applications involving Friction, Inclines

Kinetic (sliding) Friction• Friction that

opposes the motion of two objects in contact and in relative motion

4-8 Applications involving Friction, Inclines

Static Friction• Friction that

opposes the motion of two objects in contact and NOT in relative motion

4-8 Applications involving Friction, Inclines

Coefficient of friction ()• Depends on the

nature of two surfaces

= Ff Fn

• ROT s > k

4-8 Applications involving Friction, Inclines

Inclined Planes Find the force of

friction that acts on a 35 kg box that sits on a 25 inclined plane.

4-8 Applications involving Friction, Inclines

Inclined Planes Find the force of

friction that acts on a 35 kg box that sits on a 25 inclined plane.

Answer: 145N

4-9 Problem Solving-A General Approach

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