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What did I learn? Scientific Knowledge Physics 2 (Restistance (When an…
What did I learn? Scientific Knowledge Physics 2
Friction
How can we reduce Friction?
Make a surface smoother
This means there will be less of the surface catching on each other
Use a lubricant (oil or water based) to make the surface smoother
This can be seen in engines so the parts move smoothly together and do not break down
(The resistance that one surface encounters when moving over/against another)
Restistance
Resistance is what happens when an object moves through a liquid or gas
This can also be called DRAG
When an object is moving through the water it will have many different forces acting upon it
Weight
The Mass of an object
Lift
An Upward Acting force
Thrust
The force that causes an object to move forward
Drag
The resistive force caused by moving through a fluid
Buoyancy
This is the power a liquid has to keep an object floating
Submarine Example
If weight is greater than buoyancy the submarine will sink.
If Thrust is greater than Drag then the submarine will accelerate forwards and keep going until the Drag evens it out.
If Buoyancy is greater than weight it will lift upwards
If Thrust is less than Drag the Submarine will slow down.
When forces are BALANCED around an object it will move at the same rate it is already going at.
WATER RESISTANCE
Streamlining
This is the way an object is shaped in order to reduce the effects of Drag
Will an object move through the water faster if it is flat or pointed?
It will move faster when the object is pointed as it is STREAMLINED
This can be taught through experiments
For the effects of Surface area on Resistance see - Written Experiment 2
For effects of Shape in Water, see written Experiment 1 - The Effects of Shape on Drag.
Resistance
Streamlining can be applied to objects moving through air AND water E.G. Submarines and Aeroplanes
AIR RESISTANCE
Air resistance are forces that are in opposition to the relative motion of an object as it passes through the air
It is formed from an object colliding with air particles.
Objects moving through the air have similar forces acting on them as objects in the water. HOWEVER
There is no buoyancy in the air as gas is low in density
In the air, the wings of an Aeroplane generate the lift
Skydiver example
When a Skydiver jumps from the plane, initially the downward force from the weight is much greater than the force from air resistance, so the Skydiver accelerates.
He then reaches TERMINAL VELOCITY, when weight and air resistance are equal, so he falls at a constant speed
Terminal Velocity - Maximum Speed Skydiver will fall at
He then Decelerates when parachute applied because the air resistance is much greater than the downward force from weight