Forces Always pushing and pulling What is a

Forces Always pushing and pulling!

What is a force? • A force is a push or a pull exerted by one object on another object. • Forces have both a size (strength) and a direction (like velocity and acceleration). • We measure the force of an object in Newtons (N) • One Newton is the force required to lift a quarterpound hamburger

Contact Forces • Contact forces are forces exerted only when two objects are touching each other • Friction is a force that opposes the relative motion of two objects that are in contact (Smooth surfaces have smaller friction forces than rough surfaces) • Air resistance is a force exerted by air on an object moving in the air • Buoyant force is the upward force exerted by a fluid that opposes the immersed weight of an object • Normal force

Non-contact Forces • Non-contact forces are forces exerted by one object on another when the objects are NOT touching • Gravity is the pull that every object always exerts on every other object due to their mass • The force due to gravity is called gravitational force • Electrostatic • Magnetism

Gravitational Force

Mass and Weight • Mass and weight are two different measurements • Mass is the amount of matter in you • Measured in kilograms (kg) • Does not change depending where you are • Weight is the strength of gravitational force that Earth exerts on you • Measured in Newtons (N) • We usually measure weight in pounds (lbs. ) (1 lb = 4. 4 N) • Changes depending where you are

Inertia • Objects resist having their motion changed • Inertia is the tendency of an object to resist a change in its motion • Inertia is the reason why an object at rest tends to stay at rest (Newton’s First Law of Motion) • Inertia causes moving objects to move in a straight line at a constant speed • The more mass an object has, the more inertia it has https: //www. youtube. com/watch? v=qq 1 Whusk 8 No

Inertia

Combining Forces • When more than one force acts on an object, they combine. • The combination of all the forces acting on an object is called the net force • When the forces on an object are in the same direction, they are added together • When two forces on an object are in opposite directions, the net force equals the larger force minus the smaller force

Balanced and Unbalanced Forces • When the net force on an object equals zero, the forces are balanced • When the net force on object is NOT zero, the forces are unbalanced 20 N Right 20 N Left

Balanced and Unbalanced Forces • Balances forces cause an object to stay where they are. • Unbalanced forces causes an object to move (or stop moving) • The speed of an object can change • The direction an object is moving can change

Links • https: //www. youtube. com/watch? v=-F 5 nm. IJOF 4 U

References • Google Images • Florida Science Grade 6, Glencoe Science & Mc. Graw Hill Publishing