PHYS 2133
Chapter 8
Problems
Solutions
- In order convert from
degrees to radians, we must remember that 360o
= 2p
radians. Therefore, multiplying the number of degrees by 2p/360
converts the values. For the listed values, this gives:
30o
= 30o
(6.28/360o)
= .523
45o
= 45o
(6.28/360o)
= .785
60o
= 60o
(6.28/360o)
= 1.05
90o
= 90o
(6.28/360o)
= 1.57
180o
= 180o
(6.28/360o)
= 3.14
270o
= 270o
(6.28/360o)
= 4.71
360o
= 360o
(6.28/360o)
= 6.28
- If we assume that the
acceleration of the potter's wheel is constant, then we know that the wf
= wi
+ at.
Using the given data, we get:
0.20 rev/s = 0 rev/s + a(30
s)
a
= (0.20 rev/s)/(30 s) = .0067 rev/s2
We need to convert this
answer to rad/s2.
To do this, we multiply the answer by 2p/1
rev, giving
a
= (2p
rad/rev)(.0067 rev/s2)
= .042 rad/s2
- The first thing that we must
assume is that the wheels of the car are not slipping with respect to
the road. If this is the case, then we know that the angular velocity
and acceleration are given by
w
= v/r = (17.0 m/s)/(.480 m) = 35.4 rad/s
a
= a/r = (2.00 m/s2)/(.480
m) = 4.17 rad/s2
Using this data, we can
calculate the angular difference by
DQ
= (35.4 rad/s)(5.00 s) + .5(4.17 rad/s2)(5.00
s)2
DQ
= 177 rad + 52.1 rad = 229 rad
To convert this answer to
revolutions, we multiply the answer by 1 rev/2p
rad. This gives (229 rad)(1 rev/6.28 rad) = 36.5 revolutions.