Join TSR now and get all your revision questions answeredSign up now
    • Thread Starter
    Offline

    0
    ReputationRep:
    Given vector V=2i+3j-6k,find
    a) the magnitude of V
    b)the unit vector in direction of V
    c) the vector in the direction opposite to V and with magnitude 10.5
    d)the anglews which V make with the coordinate axis
    Cannot do part c) and d)

    2. Octavius the spider spins two successive threads along vectors a=i-3j+2k and b=4i+j-3k.Find
    a)the angle through which Octavius turns at the junction of the two threads
    b) the vector he must travel to form a triangular web
    c)the angle this third side makes with the x-axis
    Help in all parts
    4.Vector V makes angle 50 degrees and 70 degrees with the positive x and y directions. Find two possible valvues of V if V magnitude=6.
    Answers: 1c=-3i+4.5j+9k 1d=73.4, 64.4, 149
    2a=105 2b=-5i+2j+k 2c=156
    4)46.7 or 133.3
    THANK YOU
    • Community Assistant
    • Welcome Squad
    Offline

    17
    ReputationRep:
    (Original post by Asazycat)
    Given vector V=2i+3j-6k,find
    a) the magnitude of V
    b)the unit vector in direction of V
    c) the vector in the direction opposite to V and with magnitude 10.5
    d)the anglews which V make with the coordinate axis
    Cannot do part c) and d)

    2. Octavius the spider spins two successive threads along vectors a=i-3j+2k and b=4i+j-3k.Find
    a)the angle through which Octavius turns at the junction of the two threads
    b) the vector he must travel to form a triangular web
    c)the angle this third side makes with the x-axis
    Help in all parts
    4.Vector V makes angle 50 degrees and 70 degrees with the positive x and y directions. Find two possible valvues of V if V magnitude=6.
    Answers: 1c=-3i+4.5j+9k 1d=73.4, 64.4, 149
    2a=105 2b=-5i+2j+k 2c=156
    4)46.7 or 133.3
    THANK YOU
    1c) Take the unit vector you find in part b. If you multiply it by -1, then the vector will go in the opposite direction. If you multiply by some scalar number, that number will be the magnitude of the vector.

    1d) Take |{\bf V}|. Then quite simply the angles the vector makes between the {\bf i}, {\bf j}, and {\bf k} axis is \cos(\theta)=\frac{\text{the amount by which the vector goes along that axis}}{|{\bf V}|} then obviously you can get your angle \theta

    2a) So find the angle between the two vectors. \cos(\theta)=\frac{{\bf a}\cdot {\bf b}}{|a||b|} ring any bells?

    2b) Say the triangle is ABC with A being the position vector {\bf a} and likewise for B. Then if he travels along A, then along B, what vector must be go along to get back to A?

    2c) Same principle as 1c

    4) I dont understand the question... please elaborate?
 
 
 
Poll
If you won £30,000, which of these would you spend it on?
Useful resources

Make your revision easier

Maths

Maths Forum posting guidelines

Not sure where to post? Read the updated guidelines here

Equations

How to use LaTex

Writing equations the easy way

Student revising

Study habits of A* students

Top tips from students who have already aced their exams

Study Planner

Create your own Study Planner

Never miss a deadline again

Polling station sign

Thinking about a maths degree?

Chat with other maths applicants

Can you help? Study help unanswered threads

Groups associated with this forum:

View associated groups

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.