Remember, as a member of the Science Bus Club you can ‘Ask Albert’ a question about any of the topics. So if you’re not already a member join today!!
Some Useful Words To Remember
Friction – a force acting between two surfaces
Air Resistance – friction caused by a body moving through air
Water Resistance – friction caused by a body moving through water
Forcemeter – a piece of equipment for measuring force
Newtons – the units in which force is measured
Surface Area – the face of a body
More About Friction
Friction is the force between two surfaces rubbing together. Here are some very simple facts:
When two smooth surfaces rub together there is very little friction- When two rough surfaces rub together there is more friction
- There is less friction when there is a liquid (e.g. oil) between the two surfaces
- There is more friction if the two surfaces are forced against each other
Friction is a good thing:
Just think of walking on a wet marble floor or an icy pavement with new leather soled shoes: you might slip over! Worse still, if the tyres on your car are worn out and the road is wet and slippery, you will probably skid the car and have an accident. Both your shoes and the car's tyres need good grip so their surfaces are rough. This increases the friction between them and the ground.
Friction is also very important for your car's brakes to work properly. When you put you foot on the brake pedal, some rough pads are squeezed tight against the brake discs. This friction slows the car down. If oil gets on the discs, the brakes will not work so well.
Friction is a bad thing:
Friction inside a car engine and inside the wheel axles will slow a car down and wear out the metal. To prevent this we put oil or even grease in them. This makes their surfaces more slippery and so reduces friction.
Friction is the force between to surfaces rubbing together. It is high if the surfaces are dry and rough and it is low if the surfaces are smooth and wet.
More About Friction
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Air resistance pushes against things which are moving
- Air resistance pushes against a moving car and slows it down
- Air resistance pushes against falling objects and slows them down
Anything falling down in the air is slowed down by air resistance. The air resistance acts in the opposite direction to the weight. The gravity is larger than air resistance so the forces are unbalanced; when the spinner is let go it moves down. If an object has a large surface area when it falls to the
ground (such as a parachute), there is a large air resistance so the object falls slowly.
Click on the link buttons below to find out more about friction.
More About Water Resistance
Water resistance can refer to:
Viscosity - Viscosity is a measure of the resistance of a fluid to being deformed by either shear stress or extensional stress. It is commonly perceived as "thickness", or resistance to flow. Viscosity describes a fluid's internal resistance to flow and may be thought of as a measure of fluid friction. Thus, water is "thin", having a lower viscosity, while vegetable oil is "thick" having a higher viscosity. All real fluids (except superfluids) have some resistance to stress, but a fluid which has no resistance to shear stress is known as an ideal fluid or inviscid fluid. The study of viscosity is known as rheology.
Waterproofing - The term waterproof or water-resistant describes something that is unaffected by water or covered with a material that does not allow water in. Such items are suitable for use in wet environments (outdoors) or under water. Waterproofing or water resistance is the treatment of a surface to prevent the passage of water under hydrostatic pressure, or the process where a building component is made totally resistant to the passage of water and/or water vapor.
The hulls of boats and ships were once waterproofed by applying tar or pitch. Modern items may be waterproofed by applying water-repellent coatings or by sealing seams with gaskets or O-rings.
In construction, a building/structure is waterproofed with the use of membranes to protect contents underneath/within as well as protecting structural integrity. The waterproofing of the building envelope in construction specifications is under '07 - Thermal and Moisture' protection and includes roofing material as well as waterproofing materials.
Waterproofing is most commonly used in reference to building structures (basements, decks, flat roofs, wet areas, etc), watercraft, clothing or paper products (milk/juice cartons).
Building Your Own Forcemeter
Here’s something fun to try at home:
Purpose: To construct, calibrate and measure forces and weights using your own constructed and calibrated force meter.
Materials: Spring or elastic band, paper clips, piece of card board, tacks or staples, various known masses, various masses of unknown weights.
Procedure:
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Part A: Construction
Cut a piece of cardboard into a rectangle shape at least 4 cm by 8 cm.
- Staple an elastic band near the top of the piece of card board.
Reshape a paper clip into a hook and connect it to the other end of the elastic band.
- Attached a small piece of cardboard to the paper clip and draw an arrow on it.
Part B: Calibrating
- Hold your force meter upright with no attached masses to weigh and where ever the arrow points on the cardboard place a mark and label it with the value 0 N. (N = Newton)
- Hang a 100 g mass (weight = 1 Newton), next to where the arrow points place a mark and label it 1 N
- Repeat step 2 for a 200 g and 300 g masses ( see chart below for mass to weight conversion)
- Extend your scale the same equal amounts that the 1, 2 and 3 Newton lines and label them in 1 Newton increasing amounts
Part C: Measuring Forces using your meter
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List in the table below various unknown weights
- Estimate the weight in Newtons of each object and record in the table below
- Using your constructed force meter weigh each and record the weights in a table
Data:
Questions On Forces
Which of these surfaces will a weighted box slide across most easily?
Vinyl
Wood
Carpet
Have a go and see if you can find out the answer!!
More About Newtons
The newton is the amount of force that is required to accelerate a kilogram of mass at a rate of one meter per second squared.
More About Surface Area
Surface area is the measure of how much exposed area an object has. It is expressed in square units. If an object has flat faces, its surface area can be calculated by adding together the areas of its faces. Even objects with smooth surfaces, such as spheres, can have well-defined surface area.
The surface area of an organism is important in several considerations, such as regulation of body temperature, and digestion. Animals use their teeth to grind food down into smaller particles, increasing the surface area available for digestion.
The
epithelial (say epi-the-lial) tissue lining the digestive tract contains
microvilli, greatly increasing the area available for absorption.
Elephants have large
ears, allowing them to regulate their own body temperature. In other instances animals will need to minimize surface area, for example people will fold their arms over their chest when cold to minimize heat loss.
Some Cool Links
Click on any of the link buttons below to find out lots of more cool stuff about friction, forces and gravity.
Have fun!!!
Remember, as a member of the Science Bus Club you can ‘Ask Albert’ a question about any of the topics. So if you’re not already a member join today!!
