A force is a push or a pull that acts on an object.It has a specific direction.It has a size or magnitude. A force is a VECTOR !
How Do We Represent Forces?Force = 100 N to the right SI unit for force is SI unit for force is NEWTON NEWTON
How Do We Represent Forces? Force = 200 N to the right
Change the size and shape of objects Make Change thestationary Effects Of A Effects Of A speed of aobjects to Force On Motion Force On Motion moving body move Cause a moving body to change its direction of motion
Resultant Of Two More ForcesTwo or more forces on a body can bereplaced by a single force called theresultant force.
Newton’s First Law Of MotionNewton’s first law of motion states that an objectwill remain in a state of rest or uniform motion ina straight line unless acted upon by an externalforce.
When there is NO resultant force acting ona stationary object, it will remain at rest. Total upward force equal to total downward force
When there is NO resultant force acting onan object moving with constant velocity, itwill continue to move that constant velocityin a straight line.
Newton’s Second Law Of MotionNewton’s second law of motion states that thenet force acting upon an object is equal to theproduct of the mass and acceleration of theobject. Force = Mass x Acceleration F = ma
FrictionFriction is a force that opposes the slidingmotion between two surfaces in contactwith each other.
Frictional Force• Depends on the material in contact.• Depends on the roughness of the surfaces.• Is proportional to the force pressing the surfaces together.• Is independent of the area of contact.
Positive Effects Of Friction• Enable us to walk without slipping.• Used in brake pads to slow down the motion of vehicles.• To pick up things such as using chopsticks to pick up food.
Negative Effects Of Friction • Cause wear and tear of moving parts in machines, motors and engines. • Reduce the efficiency of engine power of cars by up to 20 %.
Ways To Reduce Friction• Using ball bearings or wheels.• Using lubricants such as oil and grease.• Use highly polished surfaces for moving parts.
Ways To Reduce Friction• Designing the shape of the vehicle to be streamlined.• Use air-cushion.