Forces Notes

A force can be a _____, a ____ or a _____. Forces can change the _____, _____ or _________ of an object

A force can be a push, a pull or a twist. Forces can change the speed, shape or direction of an object

Contact Forces Applied Force Friction Spring Force Drag - Air or water resistance Spring Force Support (or reaction) Force Tension Force

Non-contact Forces Gravity Force (or Weight) Magnetic Force Electrical Force

Balanced Forces How can I tell that the forces on an object are balanced? Not moving Constant speed Not changing shape

Unbalanced forces How can I tell that the forces on an object are unbalanced? Changing speed Acceleration or deceleration Changing direction Changing shape

Unbalanced Forces Poster Hard copy or electronic. Title "Unbalaced Forces" Choose a situation with unbalanced forces e.g.: Sky diving,Bungy jump, Race Car, Tackle, Kicking a ball, Skateboarding, Sinking Rock Find a picture to show the situation (online, from a magazine or hand drawn) Draw and label arrows to show the unbalance forces acting on the object Write a sentence that says how the unbalance forces are affecting the object (ie. changing speed, direction or shape) Do a draft or plan of the poster for Miss Voss to check before doing the final copy. 

Unbalanced Forces Skydiving The skydiver is accelerating towards the ground because the Force of gravity is greater than the force of air resistance. Skydiving

Check for Understanding For each diagram Copy it Label the force arrows Are the forces balance or unbalanced Describe what will happen to the speed of the object (same, faster, slower) and explain why.

Mass: Weight: How much matter (atoms) there is in something. Measured in grams (g) or kilograms (kg) Weight: The force due to gravity that acts on something. Measured in Newtons (N)

My Weight around the Universe   Earth (sea level) (top of Mt Everest) Moon Jupiter My Mass (kg) Force of gravity (N/kg) 10 9.8 1.66 3180 Weight (N)

Density How heavy something is for its size Density (g/cm3) = Mass (g) ÷ Volume (cm3) Mass (g) Volume (cm3) Density (g/cm3) =

Friction A force that resists surfaces sliding past each other When friction is useful: Tires on road When is friction not useful: Moving engine parts

Friction Increase friction by: Decrease friction by:

Friction Increase friction by: Decrease friction by: Rough surfaces e.g. sand paper ‘Grippy’ surfaces e.g. rubber Decrease friction by: Lubrication e.g. oil, water, wax Smooth surfaces Wheels Bearings Streamlining e.g. cars and boats

Speed Speed is how fast an object is going. Speed can is commonly measured in: kilometres per hour (kph or km hr-1) or metres per second (m/s or ms-1). Speed can be calculated by dividing the distance travelled by the time it took: Speed = distance/time

Tables an organised way to record data Title that describes what the data is Ruled columns and rows Columns or rows labelled with quantity and unit

Line Graphs a good way to present experimental data to help see patterns Title that describes what the data is Rules axes Axes labelled with quantity and unity Axes numbered in even intervals Plotted with ‘x’s