Vectors Q: Solving OR & OP | Homework Forum

[Eysz]

NOTE: Thread was moved to Homework forums and thus has no homework template...

I managed to find (a) but i couldn't figure out (b).

I think OR = OP + PR = (2/3)a + t( (-1/15)a + (2/5)b) but i don't know how to go further please guide or help me with this please. Thanks

 

[haruspex]

There's a useful, directly observable, relationship between $\vec{OR}$ and b.

 

[Eysz]

There's a useful, directly observable, relationship between $\vec{OR}$ and b.

Then i should just substitute t=10 into the OR= (2/3)a + t( (-1/15)a + (2/5)b) since the answer must be in terms of b. That would make it 4b.

Is it correct?

 

[haruspex]

Then i should just substitute t=10 into the OR= (2/3)a + t( (-1/15)a + (2/5)b) since the answer must be in terms of b. That would make it 4b.

Is it correct?

Yes, but not because you are told the answer must be in terms of b. You know from the diagram that it must be in the direction of b. Unless a and b are in the same direction, how else will you get (2/3)a + t( (-1/15)a + (2/5)b) to be a scalar multiple of b?

 

[Eysz]

Yes, but not because you are told the answer must be in terms of b. You know from the diagram that it must be in the direction of b. Unless a and b are in the same direction, how else will you get (2/3)a + t( (-1/15)a + (2/5)b) to be a scalar multiple of b?

I completely understand now! Thanks!