CH 6: Angular Velocity

Question 1

what happens in uniform circular motion

Answer 1

constant speed, but not constant velocity (because it changes direction)
velocity vector is tangent to path at point
accel. is not 0

Question 2

where does the accel. vector point

Answer 2

always towards the center of the circle

Question 3

what is used to describe angular position

Answer 3

polar coords (r, theta) instead of cartesian (x,y)

Question 4

what is the sign conventions

Answer 4

counter clockwise (ccw) = positive
clockwise = negative (cw)

Question 5

what will be used to measure theta

Answer 5

radians

Question 6

what is a complete lap around the circle

Answer 6

s = 2(pi)(r)
s is arc length

Question 7

how to convert degrees to radians

Answer 7

degree x 180 / pi

Question 8

what is arc length

Answer 8

s = r(theta)

Question 9

what is angular velocity

Answer 9

omega = difference of theta / difference of time

Question 10

what units are used for angular velocity

Answer 10

rad/sec

Question 11

what is the relationship between speed and angular velocity

Answer 11

speed = radius x angular velocity

Question 12

Two children sit on a rotating merry-go-round. Jack is
halfway between the center and the edge, while Jill is
sitting on the edge.
Which of them has the greater speed?

Answer 12

Jill because the radius is larger at the edge rather than halfway between the center

Question 13

what happens when a ball goes through a gap in a loop with an established velocity

Answer 13

it will go straight because the ball is no longer touching the hoop. the normal force between the ball and hoop is what

Question 14

what is a period, T

Answer 14

time it takes to do one revolution

Question 15

what is the relationship between angular velocity and period

Answer 15

omega = 2pi/T

Question 16

what is frequency

Answer 16

frequency, f = # of cycles/second (which also = 1/T)

Question 17

what is the relationship between angular velocity and frequency

Answer 17

omega = 2pif

Question 18

what is the units for frequency

Answer 18

hertz, Hz
ex. f=60 Hz = 60 cycles/sec

Question 19

what is rpm

Answer 19

revolutions per minute
ex. 60 rpm = 60 rev/ 60 s= 1 rev/s

Question 20

what is centripetal accel.

Answer 20

ac = v^2/r
and also
ac = r(omega)^2

Question 21

since there is an accel. that means that theres a force which points inwards

Answer 21

F = m*ac = m (omega)^2
inwards forces are positive

Question 22

what force causes centripetal accel

Answer 22

normal force usually, but also any other forces that point inwards
ex. top of a loop de loop, normal force and gravitational force points inwards

Question 23

what is apparent weight

Answer 23

normal force, its how heavy someone feels

Question 24

at the bottom of a loop de loop, what is normal force

Answer 24

N = mv^2/r + mg > mg
Wapp = N > mg

Question 25

at the top of a loop de loop, what is normal force

Answer 25

N = mv^2/r - mg so Wapp < mg

Question 26

what happens when N = 0

Answer 26

lost contact with track and is falling

Question 27

what about travelling over hills

Answer 27

N = mg - mv^2/r < mg

Question 28

what is newtons law of universal gravitation

Answer 28

F = G mM/r^2 G= the constant m, M = masses of the two obj r = distance between onj

Question 29

whats the difference between centrifugal and centripetal accel.

Answer 29

centrifugal = center fleeing (idk if this one even exists) centripetal = center seeking