Check for understanding
NASA GRACE Mission
Lumpy Earth ­ Gravity field variation...
Find the angular speed of the Earth's rotation about its axis. How does this rotation effect its shape?
Nov 5­8:33 AM
1
QQ7.7 and P. 221# 16, 21, & 51
HW Solutions
QQ 7.7 An object moves in a circular path with a constant speed v. Which is true?
c) BOTH its velocity and acceleration are changing
linear velocity 199 m/s
P. 221 # 16
angular velocity 0.05 rad/s
P. 222 # 21 Tension = Fc = 1100N
Fg = 539N The tension is about double her weight
P. 222 # 51 Tangential vel = linear velocity = 2.5 m/s2
Centripetal Acceleration ac = 7.8 m/s
Max Velocity = 4 m/s
Jan 5­11:54 AM
2
Jan 5­1:13 PM
3
The tires on a new compact car have a diameter of 2.0 ft and are warranted for 60,000 miles. a.) Determine the angle in radians through which one of these tires will rotate during the warranty period? b.) How many revolutions of the tire will the tire turn through?
A potter's wheel moves uniformly from rest to an angular speed of 1.0 rev/s in 30.0 sec. a.) Find its angular acceleration in rad/s2 b.) Would doubling the angular accel during this given period result in a doubled final angular velocity?
Nov 5­8:48 AM
4
A dentist's drill starts from rest. After 3.2s of constant angular acceleration it turns at a rate of 2.52 X 104rev/min.
a.) Determine the angular velocity in rad/sec at time = 3.2s
b.) Find the drill's angular acceleration during this time.
Nov 12­8:52 AM
5
Rotational Motion
The translation of linear quantities to angular quantities... is actually NOT so hard to do!
translation
Linear vs. Angular
Displacement
Velocity
Acceleration
Nov 12­8:12 AM
6
Nov 12­8:20 AM
7
What is the angular displacement of the following hands on a clock during one hour?
a.) the second hand
b.) The minute hand
c.) the hour hand
Nov 12­8:27 AM
8
A wheel is rotated so that a point on the edge moves through 0.50m. The radius of the wheel is 1.50m. Through what angle (in radians) is the wheel rotated?
Nov 12­8:29 AM
9
A ball has a diameter of 2.0cm. If the ball rolls 12 cm, what is the angular displacement of the ball?
Nov 12­8:37 AM
10
Angular velocity
A CD has a spiral track that starts 2.7cm from the center and ends 5.5cm from the center. The disk must spin at a constant linear velocity of 1.4 m/s.
Find the angular velocity at the beginning and end of the track.
Nov 12­8:34 AM
11
The outer edge of a truck tire has a radius of 45cm and a velocity of 23 m/s. What is the angular velocity of the tire?
A propeller spins at 1880 rev/min. What is the angular velocity in radians per second?
What is the angular displacement in 2.5 seconds?
Nov 12­8:45 AM
12
A washing machine's two spin cycles are 328 rev/min and 542 rev/min. The diameter of the drum is 0.43m.
a.) What is the ratio of fast to slow spin cycles at the surface of the drum?
Nov 12­8:50 AM
13
Angular Acceleration
Nov 12­8:56 AM
14
Jan 3­12:09 PM
15