# trigonometry

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A truck with 48-in.-diameter wheels is traveling at 45 mi/h.
(a) Find the angular speed of the wheels in rad/min.

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

• trigonometry -

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

• trigonometry -

45 mi/hr * 5280*12 in/mi /(2pi*48in/rev) * hr/60min * 2pi rad/rev = 3960 rev/min

• trigonometry -

Oops. Off by a factor of 2. I was using a radius of 48 in

• trigonometry -

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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