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A cylinder 15.0 cm in diameter rotates at 1000 rpm. (a) what is its angular velocity in rad/s? (b) what is the tangential velocity of a point on the rim of the cylinder?

Sagot :

Answer:

(a) Approximately [tex]105\; {\rm rad \cdot s^{-1}}[/tex].

(b) Approximately [tex]15.7\; {\rm m \cdot s^{-1}}[/tex], assuming that this cylinder is rotating along the axis that goes through the center.

Explanation:

The unit [tex]{\rm rpm}[/tex] stands for "revolutions per minute", where each revolution is [tex]2\, \pi[/tex] radians.

With an angular velocity of [tex]1000\; {\rm rpm}[/tex], this cylinder would turn [tex]1000\times 2\, \pi = 2000\, \pi[/tex] radians every minute ([tex]60\; {\rm s}[/tex]). Thus, the angular velocity of this cylinder would be:

[tex]\begin{aligned} \omega &= \frac{2000\, \pi\; {\rm rad}}{60\; {\rm s}} \\ &\approx 104.720\; {\rm rad \cdot s^{-1}}\end{aligned}[/tex].

A point at the rim of this cylinder would be at a distance of [tex]r = 15.0\; {\rm cm} = 0.150\; {\rm m}[/tex] from the axis of revolution of this cylinder. If the angular velocity of this cylinder is [tex]\omega[/tex], the tangential velocity of this point would be:

[tex]\begin{aligned} v&= \omega\, r \\ &= \frac{2000\, \pi}{60\; {\rm s}} \times 0.150\; {\rm m} \\ &\approx 15.7 \; {\rm m\cdot s^{-1}}\end{aligned}[/tex].