Home Page Forums School Lighthouse on the Coast


  • Lighthouse on the Coast

    Posted by Puzzle Prime on November 13, 2020 at 2:52 pm

    A lighthouse is x miles away from the coast. Its beam makes 1 revolution per minute. How fast is the beam moving along the beach, when the point on the beach it lightens up is y miles away from the point on the beach closest to the lighthouse?

    Vivek replied 1 year, 8 months ago 2 Members · 1 Reply
  • 1 Reply
  • Vivek

    November 17, 2020 at 12:33 pm

    The distance from the base of the lighthouse to the light beam is not going to change as it revolves and it is sqrt(x^2+y^2). So The speed is 2*pi*sqrt(x^2+y^2) per minute.