Practice 7E: | 1 | 2 |
3 | 4 | Go up

**T****angential speed****
- by Matt Henderson, 2003**

**1. A woman passes through a revolving door with a
tangential speed of 1.8 m/s. If she is 0.80m from the center of the door, what
is the door's angular speed? **

v_{t}= 1.8 m/s and r = 0.8 m then we use the formula v_{t}= rw

1.8 = .8 (w) so w = 2.25 rad/s

**2. A softball pitcher throws a ball with a tangential
speed of 6.93 m/s. If the pitcher's arm is 0.660 m long, what is the angular
speed of the ball before the pitcher releases it?**

** ****v _{t}
= 6.93 m/s and r = 0.660 m then we use the formula v_{t} = rw**

**
6.93 = .660 (w) so w
= 10.5 rad/s**

**3. An athlete spins in a circle before releasing a discus
with a tangential speed of 9.0 m/s. What is the angular speed of the spinning
athlete? Assume the discus is .75m from the athlete's axis for rotation.**

v_{t}= 9.0 m/s and r = 0.75 m then we use the formula v_{t}= rw

9.0 = .75 (w) so w = 12 rad/s

**4. Fill in the unknown quantities in the following table:**

**On all the problems use the formula ****v _{t} =
rw**

** v _{t
w
}**

**a. ?
121.5 rad/s
0.030 m ****
v _{t}
= .030 (121.5) so v_{t}
= 3.645 m/s**

**b. 0.75 m/s
?
0.050 m ****
.75 = .050 (w) so w
= 15 rad/s**

**c. ?
1.2 turns/s
3.8 m 1.2 turns/s * 2p
= ****7.54
rad/s then plug that into the **

**formula v _{t} = rw
and you get
v_{t }=
3.8(7.54) so v_{t}
= 29 m/s**

**d. 2.0p
m/s 1.5p
rad/s
? ****
****2.0p****
= r(****1.5p****)
so
r =
1.3 m**