# Angular deceleration of a washing machine spin cycle

Zoubayr
Homework Statement:
If you lift the lid of a washing machine during the rapid
spin–dry cycle, the cycle stops (for safety), typically after 5.0
revolutions. If the clothes are spinning at 6.0 rev/s initially,
what is their constant angular acceleration during the slowing
motion? How long do they take to come to a stop?
Relevant Equations:
w=w_o+αt
6.0 rev - 1 s
1 rev - 1/6
5.0 rev - (1/6) x 5 = (5/6) s = 0.833 s

I do not know how to calculate the angular acceleration

Gold Member
Homework Statement:: If you lift the lid of a washing machine during the rapid
spin–dry cycle, the cycle stops (for safety), typically after 5.0
revolutions. If the clothes are spinning at 6.0 rev/s initially,
what is their constant angular acceleration during the slowing
motion? How long do they take to come to a stop?
Relevant Equations:: w=w_o+αt

6.0 rev - 1 s
1 rev - 1/6
5.0 rev - (1/6) x 5 = (5/6) s = 0.833 s

I do not know how to calculate the angular acceleration
You need a second equation since you are looking to solve two unknowns, ##\alpha## and ##t##. They give you a hint by giving you the stopping distance ##\theta##.

Homework Helper
Gold Member
2022 Award
There is another equation relating angular speeds, angular acceleration and total angle. That equation does not have time in it.

Zoubayr
There is another equation relating angular speeds, angular acceleration and total angle. That equation does not have time in it.
w^2=(w_0)^2+2αθ
how to know the total angle θ?

Gold Member
w^2=(w_0)^2+2αθ
how to know the total angle θ?
The angle is given. It is 5 revolutions.

• malawi_glenn
Zoubayr
The angle is given. It is 5 revolutions.
so by using the formula: w^2=(w_0)^2+2αθ with w_0 being 6.0 rev/s, w being zero and θ being 5 we get the answer?

Gold Member
so by using the formula: w^2=(w_0)^2+2αθ with w_0 being 6.0 rev/s, w being zero and θ being 5 we get the answer?
One of the answers. How do you get the time next?

Zoubayr
One of the answers. How do you get the time next?
using this equation: w=w_o+αt with w_0 being 6.0 rev/s, w being zero and α being the value calculated from the 1st part of the question.

• bob012345
Gold Member
using this equation: w=w_o+αt with w_0 being 6.0 rev/s, w being zero and α being the value calculated from the 1st part of the question.
Note that the acceleration is a negative number from the first part giving the time as a positive number in the second part which is good.