4.1 Development of Force Concept

4.1 Development of Force Concept

• His ideas were accepted by the church and scientific community after his death.

• The first law of motion was formed by Galileo.
• The work of his predecessors enabled him to develop laws of motion, discover the law of gravity, and make great contributions to the theories of light and color.
• It is amazing that many of these developments were made without the benefit of the usual interactions between scientists today.

• It wasn't until the advent of modern physics that it was discovered thatNewton's laws of motion only produce a good approximation to motion when the objects are moving at less than the speed of light.
• The realm of classical mechanics is defined by these constraints.
• Albert Einstein and many other scientists developed quantum theory at the beginning of the 20th century.
• The constraints in classical physics do not apply to this theory.
• All of the situations we consider in this chapter are in the realm of classical physics.

• The concept of cause and effect was not always important in human thinking.
• Modern physics evolved from natural philosophy.
• The achievements of Galileo,Newton, Einstein, and others were important in the history of scientific thought.
• The work of these scientists is the basis of most of the scientific theories described in this book.

• A definition of force is needed to understand this.
• A push or pull is a good place to start.
• We know that a push or pull can have both magnitude and direction and can vary greatly in each regard.
• A cannon exerts a strong force on a cannonball that is launched into the air.
• Earth exerts a small downward pull on a flea.

• Our everyday experiences give us a good idea of how many forces are involved.
• The forces are represented by arrows and can be added using either the head-to-tail method or trigonometric methods.
• TwoDimensional Kinematics was used to develop these ideas.

• The overhead view shows two ice skaters pushing on a third.
• The total force on the third skater is shown in the direction shown.
• The free-body diagram shows the forces acting on the third skater.

• The body is represented by a single isolated point, and only those forces acting on the body from the outside are shown.
• Free-body diagrams are used extensively in the study and application ofNewton's laws of motion.