Balanced and Unbalanced Forces 11/17/15 Title Date Paga

Friction Friction – a force that opposes motion exerted by surfaces in contact.

Static friction Static friction is friction between two or more solid objects that are not moving relative to each other. For example, static friction can prevent an object from sliding down a sloped surface.

Static Friction Static Friction – the force that opposes the start of motion. Adjustable force – as the applied force increases, static friction increases. Always equal but opposite to the applied force until a maximum is reached Maximum Static friction – equal to the minimum force required to start the objects motion.

Balanced and Unbalanced Forces A force is a push or pull that causes an object to move, stop, or change direction In physics a force is anything that makes an object accelerate

Force Forces come in pairs Forces have a magnitude and a direction Magnitude: 5N Direction: north (up) 5N, north (up)

Balanced and Unbalanced Forces Forces occur in pairs and they can be either balanced or unbalanced

Balanced Forces Balanced forces do not cause change in motion They are equal in size and opposite in direction

Unbalanced Forces An unbalanced force always causes a change in motion When unbalanced forces act in opposite directions you can find the net force Net force Magnitude The difference between the two forces Direction Direction of the largest force

Unbalanced Forces 30 N, right – 60 N, left = 30N, left

Unbalanced Forces 4 N, left – 10 N, right = 6N, right

Unbalanced Forces 25 N, right + 50 N, right = 75N, right

= The sum of forces = Fnet Objects Accelerate in the direction of the net force

Force Diagram Practice Title Date Page

Sky Diver in free fall Ff Friction force on Diver by Air Fg Gravitational force on diver by earth

A book sitting on a table (at rest). Diagram the forces on the book.

Book on the table Fn Normal force on book by table Fg Gravitational force on book by earth

Bull Dog pushing a skate board Bull Dog pushing a skate board. Diagram the forces acting on the skateboard.

Skateboard pushed by dog FN Normal force on skateboard by street Ff friction force on skateboard by street Fp Pushing force on skateboard by dog Fg Dog + Fg skateboard gravitational force on skate board by earth

Dog on Ramp At rest

FN Normal force on dog by ramp Dog on ramp FN Normal force on dog by ramp friction force on dog by ramp Ff Fg gravitational force on dog by earth

FT Tension force on climber by rope FN Normal force on climber by rock Forces on Rock Climber FT Tension force on climber by rope FN Normal force on climber by rock Fg Gravitational force on Climber by earth

Ff friction force on ball by Forces on Foot Ball Ff friction force on ball by air resistance f Fg Gravitational force on Ball by earth