physics dynamics

• Kinematics: The study of motion without considering the forces that cause it.

• Dynamics: The study of forces and their impact on motion.

• Thermodynamics: The branch of physics that deals with heat and temperature and their relation to energy and work.

Newton’s laws

Newton’s first law: states that an object at rest will remain at rest, and an object in motion will continue in motion at a constant velocity, unless acted upon by a net external force.

When an object is at rest or at a constant velocity then Fnet = 0.

Newton’s second law: The acceleration of the object is inversely proportional to the mass of the object and directly proportional to the net force

F/m = a

Newton’s third law: When objects interact with each other, they exert equal and opposite forces on each other, meaning that for every action, there is an equal and opposite reaction.

action-reaction

Friction: when an object slides against other objects and provide resistance opposite to the motion

• static friction: occurs when the object is not moving and prevents motion until it is succeeded

• kinetic friction: when objects are rubbing against each other and provides resistance when there’s movement.

weight: gravitational force

scale: measures the normal force (action-reaction) to the normal person

Examples:

• in an elevator the scale will push a normal force against the person at rest

• in an elevator accelerating downward the normal force of the scale is going up and makes the person weight heavier

• in an elevator accelerating upward the scale’s normal force is going downward , resulting in the person feeling lighter due to the opposing forces acting on them. .

Tension force: applied by a string and the direction is the direction of the pull on the string