Equations (by definition) Flashcards
Write out all three equations that use acceleration, velocity, and time.
vf = vi + at
(1/2)at2+ vit + ∆x
vf2 = vi2+ 2a(∆x)
What is the equation for the measurement of the gravitational force between two objects?
F = (Gm1m2) / r2
What equation measures torque?
And what are its units?
T = rFsinθ
Torque is unitless
r is the radius of the arm
F is the force
θ is the angle of force applied
What is the equation for rotational motion?
F = (mv2) / r
What is the general equation for power?
P = (W / t)
What is the general equation for work?
W = F d cos θ
F is the force applied
d is the displacement of the object
θ is the angle between the applied force and the displacement vector
What is the total mechanical energy equation?
E = U + K
U = potential energy
K = kinetic energy
What’s the equation for momentum?
p = mv
where m is mass and v is velocity
DO NOT confuse momentum and power
What are the three equations representing impulse?
I = F∆t
(where F is force and T is time)
I = ∆p
(where p is a change in momentum, not power)
I = mvf - mvi
What does it mean in a collision if “momentum is conserved” ?
It means that the momentum before the collision is the same as the momentum after the collision
pai + pbi = paf + pbf<br></br><br></br>This is sometimes called an “elastic collision”
What is a completely elastic collision?
A collision where total kinetic energy and total momentum are conserved (there was no energy lost to heat, light, or deformation), like two objects perfectly boucing off each other
(1/2)mavai2 + (1/2)mbvbi2 = (1/2)mavaf2 + (1/2)mbvbf2
What is an inelastic collision?
Do not confuse this with “comlpetely inelastic”
When two objects collide and move away from each other, and sound/light/heat/energy is released.
(1/2)mavai2 + (1/2)mbvbi2 > (1/2)mavaf2 + (1/2)mbvbf2
What is a completely inelastic collision, and what’s the best equation to represent it?
When two objects collide and stick to each other, rather than moving apart. Total kinetic energy is not conserved.
mavai + mbvbi = (ma + mb) vf
What is mechanical advantage? What equation can be used to represent it?
Mechanical advantage = (force in / force out)
It’s the ratio of the force exerted on an object by a simple machine to the force actually applied on the machine
What’s the conversion factor of Celsius to Kelvin?
K = C + 273
What’s the equation for the measurement of thermal expansion?
∆L = aL∆T
∆L is the change in length
L is the original length
∆T is the change in temperature
a is the expansion constant
What is the equation for thermal volume expansion?
∆V = BV∆T
Where ∆V is the change in volume
V is the original volume
∆T is the change in temperature
B is the volume constant (this is 3a if given the length constant)
What is the equation for specific heat?
Q = mc∆T = mc(Tf - Ti)
Where c is the specific heat
Q is in joules
A reaction is said to be isovolumetric.
What does that mean?
Isovolumetric means that it was held at a constant volume
∆U = Q
A reaction is said to be adiabatic.
What does that mean?
The reaction had no heat exchange.
∆U = -W
A reaction is said to be in a closed cycle.
What does that mean?
Also called isothermal, it means that the temperature of the reaction stays constant.
Q = W
What is an equation for measuring entropy?
∆S = Q / T
Q is heat gained or lost
What is specific gravity?
What’s an equation to find it if given the density of an object?
Specific gravity is a density ratio. It has no units.
If given the density of an object:
specific gravity = (density of object / density of water)
What’s the equation for pressure?
What is the SI unit?
pressure = (force / area)
SI unit is Pascal
What is absolute pressure?
What is the equation for absolute pressure?
Absolute pressure is the total pressure exerted on an object that’s submerged in fluid.
P = Po + pgh
P is the absolute pressure
Po is the pressure at the surface of the fluid
p is the density of the fluid, gh is gravity x height
What is gauge pressure?
What’s an equation to calculate gauge pressure?
Gauge pressure is the measurement of the pressure in an enclosed space that is above normal atmospheric pressure
Pg = P - Patm
What is Pascal’s Principle?
What are two equations associated with it?
When a change of pressure is applied to an enclosed fluid, the pressure change will be transmitted undiminished through all parts of the fluid and the containing walls of the vessel.
P = (F1 / A1) = (F2 / A2)
F2 = F1 (A2 / A1)
What is the equation for buoyant force?
Fbuoyant = (Vdisplaced fluid)(pfluid)g
Where p is density and g is gravity