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

    0
    ReputationRep:
    Please can someone do this question for me!!! please state the equation of motion use!!!! THANKS IN ADVANCE


    A ball is projected horizontally from the top of a cliff on the surface of the earth with a speed of 40 m/s.Assuming that there is no air resistance, what will its speed be 3 s later?


    A 30 m/s

    B 40 m/s

    C 50 m/s

    D 60 m/s

    E 70 m/s
    • Community Assistant
    Offline

    20
    ReputationRep:
    Community Assistant
    You'll need to use a couple of formulae v = u + at and Pythagoras' Theorem.

    The answer is 'None of the above' unless the question also asks you to round to the nearest whole number or use a value for g that is rounded to 1 s.f.!
    • Thread Starter
    Offline

    0
    ReputationRep:
    its a multiple choice question...i think it must be round up...the answer is C in the answer booklet by the way where should i use the Pythagoras equation
    Offline

    14
    ReputationRep:
    (Original post by jinx007)
    Please can someone do this question for me!!! please state the equation of motion use!!!! THANKS IN ADVANCE


    A ball is projected horizontally from the top of a cliff on the surface of the earth with a speed of 40 m/s.Assuming that there is no air resistance, what will its speed be 3 s later?


    A 30 m/s

    B 40 m/s

    C 50 m/s

    D 60 m/s

    E 70 m/s
    Taking g as 9.81 I get the speed as 49.6601 m/s so my choice is C
    • Community Assistant
    Offline

    20
    ReputationRep:
    Community Assistant
    Ok it is against the rules to give full answers but I think you may need it in this case.

    When an object is projected and there is no air resistance, the x component stays the same (in this case it always travels at 40 m/s in the horizontal direction).

    Now consider the y component. Gravity acts downward here (they want you to use 10 metres per second squared for a). The starting velocity (u) in that direction is zero m/s. You can get the final speed in that direction by using v = u + at so v = 0 + 10 x 3 = 30 m/s.

    You now have a right angled triangle with 40 m/s in the x direction and 30 m/s in the negative y direction. The speed is the hypotenuse of this triangle (it is a 3,4,5 triangle) so the speed is 50 m/s.
    • Thread Starter
    Offline

    0
    ReputationRep:
    THANKS a lot i got the answer
    • Community Assistant
    Offline

    20
    ReputationRep:
    Community Assistant
    (Original post by jinx007)
    THANKS a lot i got the answer
    good!
 
 
 
  • 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
    Has a teacher ever helped you cheat?
  • 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

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