(Phys110) Final Exam Flashcards
what does omega stand for in rotational kinematics and what two units can it have?
> angular velocity
rad/s and rpm
what does alpha stand for in rotational kinematics and what are its units?
> angular acceleration
rad/s^2
what does theta stand for in rotational kinematics and what two units can it have?
> angular position/displacement
rads and revs
is CCW rotation positive or negative?
positive
is CW rotation positive or negative?
negative
how do you know when acceleration is negative?
when the acceleration vector points towards the negative x or y axis
how do you know when acceleration is positive?
when the acceleration vector points towards the positive x or y axis
when is torque negative?
when the force applied causes CW rotation
when is torque positive?
when the force applied causes CCW rotation
what does r stand for in the moment of inertia equation?
the distance from the mass to the axis of rotation
what does r stand for in the torque equation?
the distance between the applied force and the pivot point
what does phi (angle) stand for in the torque equation?
the angle between the applied force and the radial line
if the problem says to find the moment of inertia about an axis that is perpendicular to the page and passes through a mass, what does the axis of rotation look like?
the axis of rotation will look like an X (denoting an out-of-page axis of rotation) on top of whichever mass it’s passing through
if the problem says to find the moment of inertia about an axis that is parallel to the plane of the image and passes through two masses, what does the axis of rotation look like?
the axis of rotation looks like a line that connects the two specified masses
what is i-hat multiplied by j-hat?
positive k-hat
what is j-hat multiplied by i-hat?
negative k-hat
what is the conservation of angular momentum?
Li = Lf
initial angular momentum = final angular momentum
when you are asked “how many revolutions…?”, what are you solving for?
> theta
angular position/displacement
initial answer will be in rads, you need to convert to revs
what is the variable for density?
rho (funky p)
what is the variable for pressure?
the letter p
what kind of area is the one in the equation: p = F/A?
cross sectional area
where is there more pressure in a container filled with liquid? at the top of a container or at the bottom?
at the bottom
where is there less pressure in a container filled with liquid? at the top of a container or at the bottom?
at the top/near the surface
what creates pressure in a container filled with liquid?
gravity
what does p_o stand for?
atmospheric pressure
when a pulley has mass, what happens to tension?
unlike in previous problems, the tensions are not the same (4/11 lecture example 4)
when is torque zero?
> when there is no rotation
when the applied force is parallel to the radial line
at the pivot
when the applied force does not cause rotation
in static equilibrium problems, what should you label on the picture?
forces applied on the beam/plank/table, pivot point, distances between the applied forces and the pivot (r from torque eq), and the center of masses
what four things do you need to look for when solving for torque?
- distance between applied force and pivot (r)
- applied force of interest (F)
- angle between the applied force and the radial line (phi)
- positive/negative signs
what are the units for torque?
Nm (newton meters)
in static equilibrium problems, what forces do we care about?
only the ones that are exerted on the beam/plank/table
what is the new type of energy we learned recently?
kinetic energy for a rolling object
what is i-hat multiplied by i-hat?
zero
what is j-hat multiplied by j-hat
zero
what is the difference between the FBD of a box and the FBD of a pulley?
> FBD for box has an x and y axis
FBD for pulley is a drawing of the pulley with forces attached to it
do you need to convert to SI units when solving for the center of mass?
no but you can
do you need to convert to SI units when solving for the moment of inertia?
yes
what does “d” stand for in the pressure for an open container equation?
depth/thickness of whatever liquid(s) is in the system
when do you use bernoulli’s equation?
when there is a pipe that starts at the zero point (floor) and then reaches some new height (has an s-shape)
in which case does liquid move faster?
a. in a 4cm diameter pipe
b. in a 10cm diameter pipe
a. in a 4cm diameter pipe
> a smaller diameter means there isn’t as much pressure and the liquid will move faster than in a pipe with a bigger diameter
in which case does liquid move slower?
a. in a 20cm diameter pipe
b. in a 25cm diameter pipe
b. in a 25cm diameter pipe
> a bigger diameter means there is more pressure and the liquid will move slower than in a pipe with a smaller diameter
what is buoyancy force?
tries to make an object float in fluid
when is buoyancy force present?
whenever an object is in a liquid
when an object’s weight is greater than the fluid it displaces, what does that mean for density? Will it sink or float up?
> the average density of the system is greater than the density of the fluid
the object will sink to the bottom
when an object’s weight is less than the fluid it displaces, what does that mean for density? Will it sink or float up?
> the average density of the system is less than the density of the fluid
the object will float to the top
when an objects weight is equal to the fluid that it displaces, what does that mean for density? Will it sink or float up?
> the average density of the system is equal to the density of the fluid
the object will hang in the middle without floating up or sinking
when an objects weight is greater than the buoyancy force, will it sink or float?
the object will sink
when an objects weight is less than the buoyancy force, will it sink or float?
the object will float to the top
when an objects weight is equal to the buoyancy force, will it sink or float?
the object will hang in the middle without floating up or sinking
how do you find the period (T) on a graph?
on a graph, the period is the horizontal distance between the two peaks along the time axis (distance between the max and min point of the curve)
how do you find amplitude on a position vs. time graph?
look at the max/min points on the curve
how do you find amplitude on a velocity vs. time graph?
use the max velocity equation
> v_max = (amplitude)(angular frequency)
what two things does omega stand for?
angular frequency and angular velocity
what does phi_o stand for?
phase constant
when is the phase constant negative?
when velocity is positive
when is the phase constant positive?
when velocity is negative
when should you use energy for simple harmonic motion?
when the problem mentions an oscillating spring
when is mechanical energy converted to potential energy in simple harmonic motion?
at the amplitude (max/min position)
when is mechanical energy converted to kinetic energy in simple harmonic motion?
at the zero position
how do you convert degrees to radians?
calculator or multiply by pi/180 degrees
