(Phys110) Final Exam

Question 1

what does omega stand for in rotational kinematics and what two units can it have?

Answer 1

> angular velocity
rad/s and rpm

Question 2

what does alpha stand for in rotational kinematics and what are its units?

Answer 2

> angular acceleration
rad/s^2

Question 3

what does theta stand for in rotational kinematics and what two units can it have?

Answer 3

> angular position/displacement
rads and revs

Question 4

is CCW rotation positive or negative?

Answer 4

positive

Question 5

is CW rotation positive or negative?

Answer 5

negative

Question 6

how do you know when acceleration is negative?

Answer 6

when the acceleration vector points towards the negative x or y axis

Question 7

how do you know when acceleration is positive?

Answer 7

when the acceleration vector points towards the positive x or y axis

Question 8

when is torque negative?

Answer 8

when the force applied causes CW rotation

Question 9

when is torque positive?

Answer 9

when the force applied causes CCW rotation

Question 10

what does r stand for in the moment of inertia equation?

Answer 10

the distance from the mass to the axis of rotation

Question 11

what does r stand for in the torque equation?

Answer 11

the distance between the applied force and the pivot point

Question 12

what does phi (angle) stand for in the torque equation?

Answer 12

the angle between the applied force and the radial line

Question 13

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?

Answer 13

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

Question 14

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?

Answer 14

the axis of rotation looks like a line that connects the two specified masses

Question 15

what is i-hat multiplied by j-hat?

Answer 15

positive k-hat

Question 16

what is j-hat multiplied by i-hat?

Answer 16

negative k-hat

Question 17

what is the conservation of angular momentum?

Answer 17

Li = Lf
initial angular momentum = final angular momentum

Question 18

when you are asked “how many revolutions…?”, what are you solving for?

Answer 18

> theta
angular position/displacement
initial answer will be in rads, you need to convert to revs

Question 19

what is the variable for density?

Answer 19

rho (funky p)

Question 20

what is the variable for pressure?

Answer 20

the letter p

Question 21

what kind of area is the one in the equation: p = F/A?

Answer 21

cross sectional area

Question 22

where is there more pressure in a container filled with liquid? at the top of a container or at the bottom?

Answer 22

at the bottom

Question 23

where is there less pressure in a container filled with liquid? at the top of a container or at the bottom?

Answer 23

at the top/near the surface

Question 24

what creates pressure in a container filled with liquid?

Answer 24

gravity

Question 25

what does p_o stand for?

Answer 25

atmospheric pressure

Question 26

when a pulley has mass, what happens to tension?

Answer 26

unlike in previous problems, the tensions are not the same (4/11 lecture example 4)

Question 27

when is torque zero?

Answer 27

> 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

Question 28

in static equilibrium problems, what should you label on the picture?

Answer 28

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

Question 29

what four things do you need to look for when solving for torque?

Answer 29

1. distance between applied force and pivot (r) 2. applied force of interest (F) 3. angle between the applied force and the radial line (phi) 4. positive/negative signs

Question 30

what are the units for torque?

Answer 30

Nm (newton meters)

Question 31

in static equilibrium problems, what forces do we care about?

Answer 31

only the ones that are exerted on the beam/plank/table

Question 32

what is the new type of energy we learned recently?

Answer 32

kinetic energy for a rolling object

Question 33

what is i-hat multiplied by i-hat?

Answer 33

zero

Question 34

what is j-hat multiplied by j-hat

Answer 34

zero

Question 35

what is the difference between the FBD of a box and the FBD of a pulley?

Answer 35

> FBD for box has an x and y axis > FBD for pulley is a drawing of the pulley with forces attached to it

Question 36

do you need to convert to SI units when solving for the center of mass?

Answer 36

no but you can

Question 37

do you need to convert to SI units when solving for the moment of inertia?

Answer 37

yes

Question 38

what does "d" stand for in the pressure for an open container equation?

Answer 38

depth/thickness of whatever liquid(s) is in the system

Question 39

when do you use bernoulli's equation?

Answer 39

when there is a pipe that starts at the zero point (floor) and then reaches some new height (has an s-shape)

Question 40

in which case does liquid move faster? a. in a 4cm diameter pipe b. in a 10cm diameter pipe

Answer 40

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

Question 41

in which case does liquid move slower? a. in a 20cm diameter pipe b. in a 25cm diameter pipe

Answer 41

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

Question 42

what is buoyancy force?

Answer 42

tries to make an object float in fluid

Question 43

when is buoyancy force present?

Answer 43

whenever an object is in a liquid

Question 44

when an object's weight is greater than the fluid it displaces, what does that mean for density? Will it sink or float up?

Answer 44

> the average density of the system is greater than the density of the fluid > the object will sink to the bottom

Question 45

when an object's weight is less than the fluid it displaces, what does that mean for density? Will it sink or float up?

Answer 45

> the average density of the system is less than the density of the fluid > the object will float to the top

Question 46

when an objects weight is equal to the fluid that it displaces, what does that mean for density? Will it sink or float up?

Answer 46

> 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

Question 47

when an objects weight is greater than the buoyancy force, will it sink or float?

Answer 47

the object will sink

Question 48

when an objects weight is less than the buoyancy force, will it sink or float?

Answer 48

the object will float to the top

Question 49

when an objects weight is equal to the buoyancy force, will it sink or float?

Answer 49

the object will hang in the middle without floating up or sinking

Question 50

how do you find the period (T) on a graph?

Answer 50

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)

Question 51

how do you find amplitude on a position vs. time graph?

Answer 51

look at the max/min points on the curve

Question 52

how do you find amplitude on a velocity vs. time graph?

Answer 52

use the max velocity equation > v_max = (amplitude)(angular frequency)

Question 53

what two things does omega stand for?

Answer 53

angular frequency and angular velocity

Question 54

what does phi_o stand for?

Answer 54

phase constant

Question 55

when is the phase constant negative?

Answer 55

when velocity is positive

Question 56

when is the phase constant positive?

Answer 56

when velocity is negative

Question 57

when should you use energy for simple harmonic motion?

Answer 57

when the problem mentions an oscillating spring

Question 58

when is mechanical energy converted to potential energy in simple harmonic motion?

Answer 58

at the amplitude (max/min position)

Question 59

when is mechanical energy converted to kinetic energy in simple harmonic motion?

Answer 59

at the zero position

Question 60

how do you convert degrees to radians?

Answer 60

calculator or multiply by pi/180 degrees