A high-speed flywheel in a motor is spinning at 500 when a power failure suddenly occurs. The flywheel has mass 36.0 and diameter 75.0 . The power is off for 34.0 and during this time the flywheel slows due to friction in its axle bearings. During the time the power is off, the flywheel makes 180 complete revolutions.
At what rate is the flywheel spinning when the power comes back on?
How long after the beginning of the power failure would it have taken the flywheel to stop if the power had not come back on?
How many revolutions would the wheel have made during this time?
2007-04-15 20:27:08 · 2 answers · asked by A.J. 1 in Science & Mathematics ➔ Physics
500rpm angular velocity
2007-04-15 21:25:15 · update #1
it is 34 second
2007-04-15 22:06:39 · update #2
The rotational distance will be given by the equation
theta = w0*t - 0.5*a*t^2,
where a is the acceleration caused by axle friction, and w0 = initial velocity when the power goes off. From the given values of w0, theta and t, you can calculate a. (For 180 revolutions, theta is 180*2*π). Then use this value of a in the velocity formula:
w(t) = w0 - a*t
to find the velocity after 34 sec
The flywheel stops when w(ts) = 0, solve for ts
The no of revolutions is found from theta = w0*ts - .5*a*ts^2
revs = theta/2*π
2007-04-15 21:10:18 · answer #1 · answered by gp4rts 7 · 0⤊ 0⤋
is the 500 the velocity, or the angular velocity? Is that 34 seconds or minutes?
If it's 34 minutes, than just do 180revoution/34minutes to find the rate the flywheel is spinning when the power comes back on.
180/.34=529.41 rpm
In order to find the amount of time it takes for the fly wheel to stop, you must know the kinematic equation:
VelocityFinal=VelocityInitial+Acceleration*time
5.29rpm=500rpm+A*(.34)
A=-14.55rpm
0=500-14.55*t
t=34.36 min
Not sure if this is right..
If that is 34 seconds.. than that means the flywheel is moving faster than it normally would with the power on.. that can't be right..
2007-04-16 04:19:30 · answer #2 · answered by Mixed Asian 5 · 0⤊ 0⤋