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(Vector) How can i find the force? Please help

  1. Dec 11, 2016 #1
    • Member warned that an effort must be shown, and the homework template is required
    Hi everyone

    please help
    how can i find the force in Q(a)(ii)?

    WhatsApp Image 2016-12-11 at 9.58.01 PM.jpeg
  2. jcsd
  3. Dec 11, 2016 #2

    Andrew Mason

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    Science Advisor
    Homework Helper

    Welcome to PF William!

    A unit vector is just the vector ie. (x, y z) divided by its length. What is the length of this vector (1,1,1)?

    You must then express the force as a vector by multiplying the magnitude of tbe force (14 N) by the unjt vector in the direction of that force.

    Can you provide us with the expression for Work in terms of the information provided?

  4. Dec 11, 2016 #3
    like this?
    but how can get force of vector by multiplying
    WhatsApp Image 2016-12-11 at 11.28.24 PM.jpeg
  5. Dec 11, 2016 #4
    I did not get it. Can you please state it clearly.
    But I guess you mean how to express Force in vector form. That is simply ##{14\over\sqrt{3}}\hat{i} + {14\over\sqrt{3}}\hat{j} +{14\over\sqrt{3}}\hat{k}##.

    For (iv) you need to take dot product of (ii) and (iii). ##(\vec{A}\cdot\vec{B} = A_xB_x + A_yB_y + A_zB_z)##
  6. Dec 11, 2016 #5
    Thank you ~i got it
    i just thought the other way more complex:wink:
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