Newton’s Law of Motion {Force and Motion

Newton’s Three Laws First law (Law of Inertia) –An object at rest stays at rest and an object in motion will remain in motion with the same speed and in the same direction unless acted upon by and unbalanced force.

Newton’s Three Laws Second law (the relationship of force, mass, and acceleration) –F=ma

Newton’s Three Laws Third law (actions-reaction) –All forces occur in pairs, and these two forces are equal in magnitude and opposite in direction.

Newton’s Third Law All forces occur in pairs, and these two forces are equal in magnitude and opposite in direction. Although the forces are equal, the acceleration is not. –The more massive object has greater acceleration (due to Newton’s 2 nd law) –For example: if a basketball hits the ground, the basketball’s force on the ground is the same as Earth’s force on the basketball. Due to the ball’s much smaller mass, however, its acceleration will be much greater.

Friction What is friction? Friction is the force that exists between a piece of matter that is either moving or has a force applied to it and any other matter it is in contact with. Friction always acts in a direction opposite to that of the motion or the applied force.

Friction It was Galileo’s understanding of friction that led him to correctly assert that an object’s “natural tendency” is to keep going the same speed. From there, Isaac Newton the related his “natural tendency” aka inertia, to mass and force.

Balanced and Unbalanced Forces If the forces on an object or system add up to 0, there is not net force on the object or system. The forces are balanced. Objects that have no change in motion and could be sitting still or moving at a constant speed and direction as stated in Newton’s first law. If the forces on an object or system do not add up to zero, the object has a net force on it. The forces are unbalanced. Objects that have an unbalanced force are accelerating and have a change in motion as described by Newton’s 2 nd law.

Activity 80: Newton’s Laws of Motion You will complete a reading about forces and Newton;s three laws of motion. Then you will discuss aspects of Newton’s laws that seem to contradict daily experience.