Hey there! Sign in to join this conversationNew here? Join for free
    • Thread Starter
    Offline

    16
    ReputationRep:
    Came up on CGP Revision Guide, not sure if it's a typo.

    "Jemima is chasing a mechanised rabbit. She follows it for 50m south east, and then a further 80m west before catching it. By drawing a scale diagram, show that when Jemima catches the rabbit her displacement is 57m on a bearing of 218 degrees".

    Ok, so I drew one, and I got displacement = square root of 50sin45^2 + (80-50cos45)^2 = 57m.

    Then I got bearing = 180 + tan^-1 ([80-50cos45] / 50sin45) = 180 + 52 = 232, which doesn't equal 218 degrees. What gives?

    Thanks.
    Offline

    11
    ReputationRep:
    (Original post by Teenage Hype)
    Came up on CGP Revision Guide, not sure if it's a typo.

    "Jemima is chasing a mechanised rabbit. She follows it for 50m south east, and then a further 80m west before catching it. By drawing a scale diagram, show that when Jemima catches the rabbit her displacement is 57m on a bearing of 218 degrees".

    Ok, so I drew one, and I got displacement = square root of 50sin45^2 + (80-50cos45)^2 = 57m.

    Then I got bearing = 180 + tan^-1 ([80-50cos45] / 50sin45) = 180 + 52 = 232, which doesn't equal 218 degrees. What gives?

    Thanks.
    I don't see anything wrong with your working. I think the author mistook the other angle to find the bearing.

    218 - 180 = 38 deg

    Your angle 52 deg.

    52 + 38 = 90 deg.
 
 
 
  • See more of what you like on The Student Room

    You can personalise what you see on TSR. Tell us a little about yourself to get started.

  • Poll
    Would you like to hibernate through the winter months?
  • See more of what you like on The Student Room

    You can personalise what you see on TSR. Tell us a little about yourself to get started.

  • The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

    Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

    Quick reply
    Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.