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# Forces

Friction, Magnetism, Gravity and Electrostatic forces
by

## Joanne Mendoza

on 1 November 2012

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#### Transcript of Forces

Pushing, Pulling and Twisting FORCES Measuring Forces We measure force with a unit called 'Newtons'
We can measure the size of a force using a spring balance
Force diagrams indicate the direction and magnitude (strength) of the force
If there are more than one force acting upon an object, we can calculate a NET FORCE to determine what movement results Identify as many forces in the following scene
Pick one force. Draw a snapshot of what is happening in the scene and add force arrows to indicate the direction AND magnitude of the force A force that acts against any force.
It slows and stops all moving objects Friction No calling out, thanks! Identify the objects experiencing friction Car vs. Air resistance
Axles vs. Wheels
Any others? Identify the pairs of objects experiencing friction Adv. Disadv. Aim:
Equipment:
30cm ruler
Rubber band
Mass carrier and masses
Method:
Calibrate your force measurer by setting up the equipment as shown in the diagram below: (Draw a diagram)
Record the length in which 100g pulls the elastic to
Measure the size of the following forces.
Force needed to open the door
Force needed to drag a chair across the floor
Force needed to open a drawer in the laboratory
Force needed to move your pencil case
Force needed to pull up your sock
Record these measurements in your results table Experiment to measure forces Don’t forget to write a conclusion! This must reflect your AIM What must be included in a discussion?

Explanation of results
Reliability, Validity and Accuracy of results
Problems with the experiment AND how they can be improved in the future
Suggestions for other experiments we can do that will reinforce our understanding of the concept Discussion Friction How can we reduce friction... ... caused by air or water resistance?

... caused by objects rubbing against each other? The natural force of attraction exerted by a celestial body, such as Earth, upon objects at or near its surface, tending to draw them toward the center of the body. Gravity Let's Review Define Friction
What are some advantages of friction?
What are some disadvantages of friction?
How can we reduce friction caused by air resistance?
How can we reduce friction caused by objects rubbing together? Gravity Aristotle Newton Galileo Different
perspectives Aristotle held that objects move toward their natural place, and that this natural motion would proceed unless hindered All objects accelerate by gravity at the same speed Strength of the gravitational force decreases as distance increases
Objects with more mass have stronger gravitational fields force of attraction or repulsion between various metallic substances, especially those made of iron, nickel and cobalt. Magnetism Copy out the practical activity, 'Attracting and Repelling' on page 240 of Science Focus.

Collect your materials and answer the questions at the end. Exploring Magnets Forces in Water Scenario: you are all maritime engineers competing to design Australia's next freight ship. The government only has enough money to fund one new design. Who's will it be?

Being a freight ship, the design must carry the most weight without sinking. Your prototype must be built using EITHER:

one A4 sheet of paper
one A4 sheet of aluminium foil
one A4 sheet of Cellophane The Paper Boat Challenge INVESTIGATION STATIONS For each activity, you must answer the questions at the station. There are two activities set up around the room. Each activity has a set of instructions. You will have 25 minutes to complete each activity. When the buzzer goes off, you must move on to the next station Word Bank Forces: something that changes motion. this can be either a push, pull or twist.
Acceleration: the motion of an object increasing speed due to the application of a force
Deceleration: the motion of an object slowing down due to the application of a force
Direction: The orientation in which a force is applied
Deformation: a change in the shape or size of an object due to an applied force The Egg Drop Challenge
Design a device that will save Mr Dumpty from a fall off the balcony outside the Library. You are supplied with the following materials:
cotton wool, foam cups, sawdust, egg carton, bubble wrap, newspaper, plastic bags, paper, shredded paper, packing foam and sponges
You are allowed to bring extra materials from home in on Thursday Can you save Humpty Dumpty? You will need to:
draw a design for a prototype and have it approved by Miss Mendoza
write a list of materials you will use and how much you need Reflect Which designs worked? Why?

What other features could we have included to improve the design?

Provide five adjectives that describe an effective design? Modern Family: Season 3, Episode 12 Measuring Friction SF1 p216 The Wonky Tower Challenge http://www.media.pearson.com.au/schools/cw/au_sch_whalley_sf1_1/int/7_forces.html Let's Test this Out! Predict!
Observe!
Explain! Which object will fall first? What is the difference between weight and mass? How do we measure each thing? Pack it up! Measuring Mass and Weight: SF1 p 223 What do you think the word 'Mass' means? What do you think the word 'Weight' means? Mass: the amount of matter in an object, or the amount of space an object takes up. This is measured in grams (g), kilograms (kg) or tonnes (t) Weight: the name given to the pulling force on a
mass caused by gravity. In other words, it depends on mass AND gravity (weight = mass x gravity). Weight is measured in Newtons (N) because it is a force. You have 15 mins to build a tower out of the given materials, such that it can hold a marshmallow at the top for at least 10 secs.

Materials:
12 pieces of spaghetti