Hey there! Sign in to join this conversationNew here? Join for free
x Turn on thread page Beta
    • Thread Starter
    Offline

    2
    ReputationRep:
    A physics lecture theatre is situated 3m east and 4m above reception. Calculate the minimum energy a 60kg receptionist would have to expend to reach the lecture theatre.
    A 1800J
    B 2400J
    C 3000J
    D 4200J

    the answer is b due to mgh but why doesn't kinetic energy come into it to move 3m east?
    Offline

    20
    ReputationRep:
    (Original post by runny4)
    A physics lecture theatre is situated 3m east and 4m above reception. Calculate the minimum energy a 60kg receptionist would have to expend to reach the lecture theatre.
    A 1800J
    B 2400J
    C 3000J
    D 4200J

    the answer is b due to mgh but why doesn't kinetic energy come into it to move 3m east?
    What's the minimum kinetic energy at the end?
    Offline

    7
    ReputationRep:
    (Original post by runny4)
    A physics lecture theatre is situated 3m east and 4m above reception. Calculate the minimum energy a 60kg receptionist would have to expend to reach the lecture theatre.
    A 1800J
    B 2400J
    C 3000J
    D 4200J

    the answer is b due to mgh but why doesn't kinetic energy come into it to move 3m east?
    Hello,

    In this question, one should only consider the change in GPE. This is the minimum required energy to move 4m in the vertical direction. As for the horizontal direction, we do not know the minimum force required by the receptionist and therefore cannot calculate the work done in that respect (E = Fd). We therefore assume that the force required is negligible (horizontally) and so there is a 0J contribution from the horizontal motion. I hope that this has helped.
    • Thread Starter
    Offline

    2
    ReputationRep:
    (Original post by Smithenator5000)
    Hello,

    In this question, one should only consider the change in GPE. This is the minimum required energy to move 4m in the vertical direction. As for the horizontal direction, we do not know the minimum force required by the receptionist and therefore cannot calculate the work done in that respect (E = Fd). We therefore assume that the force required is negligible (horizontally) and so there is a 0J contribution from the horizontal motion. I hope that this has helped.
    ok thanks
    Offline

    7
    ReputationRep:
    (Original post by runny4)
    ok thanks
    You're welcome.
 
 
 
Poll
Do you agree with the proposed ban on plastic straws and cotton buds?

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.