Grade 8 Physics Past Paper PDF - Paranaque Science High School

Paranaque Science High School S.Y. 2019-2020 GRADE 8 First Quarter INFORMATION...

Paranaque Science High School S.Y. 2019-2020 GRADE 8 First Quarter INFORMATION SHEET Force and Newton’s Laws of Motion FORCE, F Force, F is a push or pull exerted by one body on another body. Net force is a physical quantity that can change an object’s state of motion, whether to: a. STOP or START motion b. SPEED UP or SLOW DOWN c. CHANGE DIRECTION of the moving object. REPRESENTING FORCES Force, as a vector quantity can be represented through an arrow. Arrows are used as force diagrams to represent forces acting on objects. Remember that: SIZE is synonymous to MAGNITUDE or VALUE of the force applied. Also, remember to always label the forces the arrows represent and their sizes in newtons (N). The newton (N) is the standard unit for force, named after the English physicist and mathematician Isaac Newton. BALANCED AND UNBALANCED FORCES Balanced Forces Unbalanced Forces Forces are balanced when two forces acting on an Forces are unbalanced when two (or more) forces object are of the same size and act in opposite acting on an object are not equal in size. This means directions. In this scenario, the resultant force is that the resultant force is no longer zero. zero. Unbalanced forces cause changes in the state of The resultant force is the overall force acting on an motion of an object. object when two or more forces are combined.  LAWS OF MOTION Sir Isaac Newton was the one credited to formulate the laws of motion. These laws are called Newton’s Laws of Motion. First Law of Motion (Law of Inertia) Aristotle thought that an object needs a force to keep it moving. A rolling ball always comes to a stop. It needs a force to keep moving. Galileo thought that a force is not needed to keep an object moving. He argued that the ball stops because it is acted upon by friction between the ball and the surface. If there is no friction the ball will continue to move. However, Newton came and explained thoroughly this phenomenon. He formulated the first law of motion. Inertia (according to Galileo) is the tendency of an object to maintain it original state of motion (at rest or in motion). Mass is the measure of inertia. “an object at rest will remain at rest; an object in motion will continue to move; unless acted upon an unbalanced force” Second Law of Motion (Law of Acceleration) Force causes the motion of an object. However, with varying masses, applied force also differs, thus results to different behavior of motion. According to Isaac Newton, the force applied and mass are factors to make an object move (accelerate). Thus, “the acceleration of an object is directly proportional to the net force and inversely proportional to the mass of the object” Mathematically, the second law can be expressed as 𝑭 = 𝒎 𝒙 𝒂, where F is force in Newton (N), m is mass in kilogram (kg) and a is acceleration in meter per second square (m/s2). Third Law of Motion (Law of Interaction) Mathematically, 𝐹𝑎𝑐𝑡𝑖𝑜𝑛 = −𝐹𝑟𝑒𝑎𝑐𝑡𝑖𝑜𝑛