Term 1 Flashcards
Define a radian
angle subtended at the centre of the circle by an arc of equal length to the radius of the circle
State the formulas for angular velocity
w = 2pi /T
w = change in angle/ change in time
State the formulas for velocity, acceleration and force in circular motion
v = wr a = wv a = v^2/r F = mv^2/r F = mrw^2
State Newton’s law of gravitation
Two point masses attract each other with a force that is directly proportional to the product of their masses and inversely proportional to the square of their separation:
F = G x Mm/r^2
Define gravitational field strength
Gravitational force exerted per unit mass at a point:
g = GM/r^2
Define gravitational potential and explain why it is negative
Work done per unit mass in bringing a mass from infinity to a point.
potential = -GM/r
- g.p.e is zero at infinity and decreases as you move closer to another mass
- this means that potential is always less than zero
Define simple harmonic motion
motion in which acceleration is directly proportional to displacement and in the opposite direction to displacement:
a = -w^2 x
State the formulas of s.h.m
if starts at 0 : x = x0 sin wt
v = v0 cos wt
if starts at max: x = x0 cos wt
at any point: v = ± w √x0^2 - x^2
Total energy = 1/2 k A^2 , 1/2 mw^2A^2
Define damping and resonance
Damping: Dissipation of oscillators energy due to resistive forces
Resonance: A phenomenon that occurs when the forcing frequency matches the natural frequency of the system, increasing the amplitude
Explain how ultrasound imaging occurs
- Electrical signal → Mechanical movement through transducer as piezo crystals change shape.
- Crystal resonates
- Damping material used to stop the oscillations of teh crystal so reflected waves can be detected
- Reflected waves change shape of crystals causing electrical oscillations.
- Electrical oscillation can be put on display
State the formulas for impedence, reflection strength and attenuation
Impedance = density x speed of sound in material
Reflected intensity/Original intensity = (z2 - z1)^2/(z2 + z1)^2
Intensity = Original intensity x e^ - attenuation coefficient x distance moved by wave.
Define internal energy
The sum of the random distribution of kinetic and potential energies of its atoms and molecules.
Define temperature
The average kinetic energy of the particles in a body
State the first law of thermodynamics
Increase in internal energy = energy supplied by heating + energy supplied by doing work
Define specific heat capacity and specific latent heat
Specific heat capacity: Energy required per unit mass to raise temp by 1 K
E = mcΔT
Specific latent heat: Energy required per kilogram to change state
E = mL
