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Math- Trig please help!

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A tire with a diameter of 100 cm rotates 20 times in 3 seconds.
a) determine the angular velocity
b) how far the tire has travelled?
c) what is the speed in km/h?

  • Math- Trig please help! - ,

    a) angular velocity = 20(2π)/3 radians per second
    = 40π/3 rad/sec

    b) one rotation = (2π)(50) cm = 100π cm
    so 20 rotations would cover 20(100π) or 2000π cm

    c) assuming you mean linear speed
    speed = distance / time = 2000π/3 cm/sec
    = (2000π/3)(3600)/(100000) km/h
    = 24π km/h

    ( there are 100000cm in 1 km, and 3600 seconds in 1 hour)

  • Math- Trig please help! - ,

    angular velocity is radians/sec

    20rev/3sec = 20/3 rev/sec = 40pi/3 rad/sec

    Assuming that the tire rolls without slipping, it has gone 20*2pi*100 = 4000pi cm

    4000pi cm/3sec = 4188.8cm/sec * 3600sec/hr * 1km/100000cm = 150.8km/hr

  • Math- oops - ,

    My bad. I missed where it said diameter, not radius.

    Reiny has it right.

  • Math- Trig please help! - ,

    thank you!

  • Math- Trig please help! - ,


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