# Rotational Motion WS

```Physics IB-1
Rotational Motion Worksheet
1. The Andromeda galaxy is a giant spiral-island whose mass is that of 300 thousand million suns. It
subtends an angle of 4.1o and is known to be larger than our own galaxy at 163 000 light-years
across. How far away is this galaxy?
2. A decent spy-satellite camera can distinguish that subtends angles of little as 0.5 x 10-6 rad. How
small an object could such a device detect from 300 km away?
3. A very fast horse can complete a 1500 m race around a circular track in a time of 92.2 s.
a. What was the horse’s average linear speed?
b. What was the horse’s average angular speed?
4. The platter of a computers’ of a high speed hard drive spins at 10 000 rpm.
a. What is the angular velocity of the platter?
b. What is the linear speed of the platter at its speed at appoint 5.00 cm away from its
center of rotation?
c. If a single bit of information requires 0.50 µm of length along the direction of motion,
how many bits per sec. can the writing head write when it is 5.00 cm from the axis?
5. A horizontal cylinder with a radius of 0.75 m has a rope wrapped around it that supports a
weight at its end as shown. At what constant angular speed must the shaft rotate if the weight is
to descend at 1.5 m/s?
ω
R = 0.75 m
v = 1.5 m/s
6. At a particular moment in a race, a car roaring around a turn with a radius of 75 m had an
angular speed of 0.65 rad/s and an angular acceleration of 0.23 rad/s2.
a. What is its linear speed?
b. What is its centripetal acceleration?
c. What is its tangential acceleration?
7. It takes 30.0 s for the shaft of a big electric motor to reach 500 rev/sec. What is its average
angular acceleration?
```
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