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P5
P5
Force is a
vector quantity
What do vectors have
Direction and magnitude. Force, velocity, displacement, acceleration, momentum
What do scalar have
Direction. Speed, distance, mass, temperature, time
A force can be a
push or a pull
When two objects have to be touching for a force to act,
that force is called a contact force.
If the objects do not need to be touching for the force to act,
the force is a non
Name some contact forces
Friction, air resistance
Name some non
contact forces
What is weight?
The force acting on an object due to gravity.
Weight =
Mass (Kg) x Gravitational Field Strength (N/kg)
What is the resultant force?
It is the forces combined to show the result of the overall force.
When a force moves an object through a distance,
energy is transferred and work is done.
Work Done (J) =
Force (N)x Distance (m)
If forces acting on an object combine to give a resultant force of zero:
the object is in equilibrium.
If a object is elastically deformed
it can go back to it's original shape and length after the force has been removed.
An object has been inelastically deformed
if it doesn't return to it's original shape and length after the force has been removed.
(For springs) Force (N) =
Spring constant x Extension
What is the spring constant?
How stiff the spring is, the stiffness depends on the material used.
On a spring constant graph, what does a curve show?
It shows the extension is no longer proportional to force.
The point where the extension is no longer proportional to the force is the
limit of proportionality
Work done in stretching a spring can be found using this equation:
E = 1/2 x ke^2 or Elastic potential energy
Speed is
how fast you're going with no regard to the direction.
Velocity is
a speed in a given direction
Acceleration is the
change in velocity in a certain amount of time.
Word equation for acceleration:
Acceleration (m/s^2) = change in velocity (m/s) / Time (s)
Constant acceleration is sometimes called
uniform acceleration.
Velocity
time Graph
What can reduce friction?
Lubcricant
What is drag?
The resistance you get in gas or luquid.
What does a fluid represent?
A gas or a liquid
What is the best way to reduce Drag,
steamlining the object.
What does steamlined mean?
This is where the object is designed to allow fluid to flow easily across it, reducing drag.
Objects with large surface areas tend to have
lower terminal velocities.
What is Newton's First Law?
If the resultant force on a stationary object is zero, the object will remain stationary. If the resultant force on a moving object is zero, it'll just carry on moving at the same velocity.
Acceleration is
inversely proportional to the mass of the object.
What is the formula for Newton's second law?
F = ma, Resultant force (N) = Mass (kg) x Acceleration (m/s^2)
What is inertia?
This is the tendency to continue in the same state of motion.
A objects inertial mass
measures how difficult it is to change the velocity of an object.
To find the inertial mass you use
m = F / a
Newton's Third Law says:
When two objects interact, the force they exert on each other are equal and opposite.
If two people push on each other,
the person will the smaller mass will move further due to a = F / m
Stopping distance =
Thinking Distance + Breaking Distance
What is the Thinking Distance?
The distance travels during the driver's reaction time.
What is the Breaking Distance?
The distance taken to stop under the breaking force.
What is thinking distance affected by?
Your speed. Your reaction time.
What is braking distance affected by?
Your speed, The weather or road surface, Conditions of tyres, Quality of brakes.
When the brakes are pressed:
The break pads are pressed onto the wheels, this contact causes friction, which causes work to be done. This work transfers kinetic energy into the thermals stores in the breaks.
Momentum (Kg m/s) =
mass (kg) x velocity (m/s)
What is the conservation of momentum?
In a closed system, the total momentum before an event is the same after the event.
If something collided to gain mass the
momentum would be the same but the velocity would decrease.
P6
P6
What is the amplitude of a wave?
The maximum displacement of the point on the wave from its undisturbed position.
What is the wavelength?
The distance between the same point on two adjacent waves.
What is Frequency?
The number of complete waves passing a certain point per second.
What can you calculate from frequency and how?
You can find the period of a wave using period (s) = 1/(frequency)
What is a transverse wave?
This is where the oscillations are perpendicular (90 Degrees) to the direction of energy transfer.`
Name three examples of transverse waves:
All electromagnetic waves, Ripples and waves in water. A wave on a string.
What is a longitudinal wave?
The oscillations are parallel to the direction of energy transfer.
Name a longitudinal wave?
Sound waves in air.
What is the wave speed?
The speed at which energy is being transferred
Wave speed (m/s) =
Frequency (Hz) x Wavelength (m)
When a wave meets a boundary between materials three things can happen:
The wave is absorbed by the sedcondmaterial e.g. the wave transfers energy to the materials energy stores.
The wave is transmitted through the second material, often leads to refraction.
The wave is reflected (sent back)
Electromagnetic waves
transfer energy from a source to an absorber.
EM waves aren't vibrations in particles,
they're vibrations of electric and magnetic fields.
They travel at different speeds in
different materials.
If a wave is travelling along the normal it will change speed but
is not refracted.
If a wave is travelling at a angle,
it changes direction (refracted)
If it bends towards the normal it
slows down and if it bends away from it speed sup.
What is the main reason in the change of speed?
The density of the two materials.
When the wave is refracted, the wave length changes but
the frequency remains the same.
What waves do satellites use to communicate?
Microwaves
Microwaves use microwaves that are
absorbed and transfer energy into the water molecules of the food, causing the water to heat up, this then transfers energy to the rest of the food.
More infrared radiation is given out by
hotter objects.
Infrared cameras can be used to
detect infrared radiation and monitor temperature.
A infrared camera works by
detecting the IR radiation and turning it into a electrical signal which is displayed.
IR radiation is
absorbed to warm objects.
Optical fibres work because of
reflection, the light rays are bounced back and forth until the reach the end of the fibre.
Why is visible light used in optical fibres?
because it's easy to refract so that it stays in a narrow fibre.
It's not easily absorbed or scattered.
Fluorescence is a property of certain chemicals, they
absorb UV light and emit visible light, this is done by a layer of phosphorus.
Fluorescence lights
energy efficient so there good for when light is needed for long periods.
Security pens can be used to
mark property with you name to help identify your property.
Ultraviolet radiation gives you
suntan
What do Radiographers take in hospitals?
x
X
rays
X
rays and gamma rays are used to
Why are X
rays and Gamma rays used to treat people with cancer?
Gamma radiation can also be used as a
medical tracer.
A medical tracer is where a
gamma
Why is gamma radiation well suited as a medical tracer?
It can pass out through the body to be detected.
Leslie Cube particle:
Step 1: Place the empty leslie cube on a heat
Step 2: Boil water in a kettle and fill the leslie cube.
Step 3: Wait, then hold a thermometer against each of the four vertical sides.
Step 4: Hold an infrared detector a set distance away and record the amount of IR radiation it detects.
Step 5: Repeat measurement on all faces.
Step 6: Repeat the experiment.
The thermometer temperature should
be the same on all four faces.
Note
Flashcard