Mechanics and waves Flashcards
What is the centre of gravity
A point on the object where gravity appears to act generally in the middle but not always
Why is a tall glass easily toppled
It is easily toppled when the line of action of its weight is beyond the edge of the base then the glass tips right over
Definition of moment
The product of the force * the perpendicular distance from the pivot
What is the eqaution for moments
Moments = FD
What is the pivot point
The point of Whitchurch an object rotates about
How do you know when an object is equilibrium
When the sum of clockwise moments equals the sum of anti-clockwise moments and there is no resultant force
How would you calculate the centre of mass of a piece of card
Hang up the card and suspend a plumb line from the same place
Mark the position of the thread
Repeat the above steps with the card suspended from different places
Where these lines intersect is the centre of mass
Definition of equilibrium
No resultant force
No resultant moment
What is the eqaution for momentum
P = mass * velocity
How do you work out velocity.
Total distance / total time
How do you work out GPE
GPE = MGH
How do you work out Ke
1/2 Mvsqaured
What is a scalar measurement
An amount just with a magnitude
Energy work done
Distance around a circle
What is vector measurement
An amount with a direction
Distance you are form the start of circle
What is an example of a scalar measurement
Speed
What are examples of vector measurements
Displacement
Force
velocity
Acceleration
What is the change in momentum also called
An impulse
How can you calculate F
F= impulse/time
What is the equation for momentum
Mass * velocity
What are the three conservation laws
Conservation of energy
Conservation of moments in equilibrium
Conservation of momentum
What does the conservation of energy state
The total energy after something happens is equal to the total energy before something happens
What does the conservation of moments in equilibrium state
Anti-clockwise moments are equal to clockwise moments
What does the conservation of momentum state
The total momentum before something is happening is eqaul to the total momentum of something after it happens
How do you calculate the distance from a graph
Area under the graph
What is the spring extension in terms of measured length and original lengthe
Measured length - original length
How do you know when an object is in equilibrium
If it’s centre of mass is vertically above the pivot point
Definition of equilibrium
Resultant force on something is zero and the resultant, turning affect on something is zero
What happens to the acceleration of a stone when it falls
Celebration stays the same never increasing or decreasing the velocity increases while gravity is 9.8
Definition of amplitude
From the average position of the crest or distance, measured from average position to the trough
Definition of wavelength
The distance between two corresponding points on the wave and is measured in metres
Definition of frequency
This is how many waves pass by every second and is measured in hertz
Definition of transverse waves
When the displacement is it, a right angle to the direction of the wave is energy travelling
Definition of longitude waves
When the displacement is parallel to the direction of the wave
How do you calculate the wave velocity?
Frequency * wavelength
What are wave describes as around a fixed point?
Oscillation and vibration
What are examples of oscillation and vibration Waze?
Ripples cause particles of water to oscillate up and down sound waves cause particles of a to vibrate back and forth
The toy dog bobbing up and down on top of the surface of some water as waves pass it underneath, explain how the toy dog demonstrates that we do not transfer matter
Step one identified the wave.
The type of wave on the surface of a body of water is a transverse wave, because the duck is moving perpendicular to the direction of the wave step to describe the motion of the toy doc, the plastic duck moves up and down, but does not travel with the wave step three explain how this motion demonstrates the waves do not transfer matter both transverse and longitudinal waves transfer energy but not the particles of the medium. This means when a wave travels between two points no matter actually travels with it the points on the way you just vibrate back-and-forth about fix positions objects floating on the water that simply pop up and down when the waves pass underneath them, demonstrating that there is no movement of matter in the direction of the wave only energy.
What is the definition of defimition
When the displacement is it, a right angle to the direction of the waves energy travelling
What is three processes of waves when they interact with other objects
Reflection, refraction diffraction
What is the law of reflection?
The angle of incidence equals the angle of reflection
How do you find the angle of incidence?
Always measured from the ray to the normal
How do you mark the normal?
It is always at a right angle to the boundary
In refraction flight goes on from the normal what happens to it?
It’s slows down then speeds up, but doesn’t bend because doesn’t go in at an angle
What happen when waves across a Boundry and slow down
Play Ben towards does a normal
What happens to the beam after the change in angle from a refraction?
the frequency stays the same wavelength before is bigger than the wavelength after the velocity before is greater than the velocity after
What is a medium?
Something the waves will travel through
What is the difraction?
Maximum the fraction is the weather like disperses greatly after going through a gap in the wall. If the gap is small, you get maximum diffraction, but if the gap is big, you get minimum diffraction
