Chapter 5 Newton’s laws of motion Dr. Haykel Abdelhamid Elabidi 1 st week of November 2013/DhH/Muh 1434

Units of Chapter 5 Force and mass Newton’s first law of motion Newton’s second law of motion Newton’s third law of motion Contact force

Force and mass A force is a push or a pull. The force is a vector (defined by its magnitude and its direction). The mass of an object is a measure of how difficult it is to change its velocity: It is more difficult to stop a car than to stop a baseball. The mass can also be defined as the measure of the quantity of matter in an object.

Newton’s first law of motion An object at rest reamains at rest as long as no net force acts on it An object moving with constant velocity continues to move with the same velocity (same speed and direction) as long as no net force acts on it. In order to change the velocity of an object –magnitude or direction – a net force is required. If the net force on an object is zero, its velocity is constant.

Newton’s second law of motion Acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass. Acceleration is inversely proportional to mass Acceleration is proportional to force These observation give: or If an object have several forces acting on it; the acceleration is due to the net force (sum of force vectors): The force is a vector, we can find its components:

Newton’s second law of motion Exercise 5-1 p116:

Newton’s third law of motion when two bodies interact, the force which body "A“ exerts on body "B" (the action force ) is equal in magnitude and opposite in direction to the force which body "B" exerts on body "A" (the reaction force). (the law of action-reaction)

Weight and normal force

Newton’s laws of motion Example 5-1 p119:

Example 5-2 p121: Newton’s laws of motion 1 mi =1609 m

Newton’s laws of motion Example 5-3 p123:

Contact force

Thank you for your attention See you next time Inchallah