Posted by **monic** on Monday, November 26, 2012 at 11:35pm.

A truck with 48-in.-diameter wheels is traveling at 45 mi/h.

(a) Find the angular speed of the wheels in rad/min.

rad/min

(b) How many revolutions per minute do the wheels make?

rev/min

- trigonometry -
**Reiny**, Monday, November 26, 2012 at 11:42pm
one rotation = 2π(48) = 96π inches

in 1 hour it goes 45 miles

= 45x5280x12 inches

= 2851200 inches

number of rotations per hour

= 2851200/(96π) = 9453.8.. rotations per hour

= 157.563 rpm

= 157.563x(2π) radians /min

= 990 radians/min

- trigonometry -
**Steve**, Monday, November 26, 2012 at 11:45pm
45 mi/hr * 5280*12 in/mi /(2pi*48in/rev) * hr/60min * 2pi rad/rev = 3960 rev/min

rev/min = rad/min * rev/2pi rad, so divide 3960 by 2pi

- trigonometry -
**Steve**, Monday, November 26, 2012 at 11:47pm
Oops. Off by a factor of 2. I was using a radius of 48 in

- trigonometry -
**Reiny**, Monday, November 26, 2012 at 11:53pm
Rats, I read it wrong also

radius should have been 24 , not 48

make the necessary adjustments in the above.

(time to go to bed)

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