A wheel with radius 32 cm is rotating at a rate of 14 rev/sA wheel with radius 32 cm is rotating at a rate of 14 rev/s(a) What is the angular speed in radians per second?(b) In a time interval of 5 s, what is the angle in radians through which the wheel rotates?(c) At t=10 s the angular speed begins to increase at a rate of 1.3 rad/s/s. At t=15 s, what is the angular speed in radians per second?

Respuesta :

(a) 88.0 rad/s

The angular speed of the wheel is

[tex]\omega = 14 rev/s[/tex]

Keeping in mind that

1 revolution = [tex]2\pi[/tex] radians

The angular speed in radians/second can be found by solving the proportion:

[tex]14 rev/s : x = 1 rev : 2 \pi rad[/tex]

From which we find

[tex]x=\frac{14\cdot 2 \pi}{1}=88.0 rad/s[/tex]

(b) 440 radians

Assuming the wheel is rotating at constant angular speed, the angular displacement of the wheel at time t is given by

[tex]\theta= \omega t[/tex]

where

[tex]\omega=88.0 rad/s[/tex] is the angular speed

t is the time

Substituting

t = 5 s

we find the angle through which the wheel has rotated after 5 seconds:

[tex]\theta=(88.0)(5)=440 rad[/tex]

(c) 94.5 rad/s

The angular speed after a time t is given by

[tex]\omega(t) = \omega_o + \alpha t[/tex]

where

[tex]\omega_0=88.0 rad/s[/tex] is the angular speed at t=10 s, when the acceleration starts

[tex]\alpha = 1.3 rad/s^2[/tex] is the angular acceleration

The duration of the acceleration is

t = 15 s - 10 s = 5 s

So substituting this value into the equation, we find the new angular speed:

[tex]\omega(15) = 88.0+(1.3)(5)=94.5 rad/s[/tex]