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# M1 vector help Watch

1. A particle moving with speed Vms-1 in direction d has velocity vector v. find v
1) V = 10, d = 3i-4j

I'm confused on what it actually wants us to work out. Thanks
2. the V they give you is the magnitude of the velocity vector you need to find it in vector form.

I think..
3. (Original post by thelion0)
the V they give you is the magnitude of the velocity vector you need to find it in vector form.

I think..
so how would i go about working it out?
4. (Original post by physicshelpme)
so how would i go about working it out?
Is that all that the question asked?
5. The velocity vector is going in the same direction as the directional vector; in other words, the velocity vector is the directional vector 3i-4j multiplied by some scalar such that the magnitude of the velocity vector is V=10.

Do you see what you need to do yet?

Hint: What's the modulus of 3i-4j?
6. (Original post by thelion0)
Is that all that the question asked?
yea that was everything
7. (Original post by aznkid66)
The velocity vector is going in the same direction as the directional vector; in other words, the velocity vector is the directional vector 3i-4j multiplied by some scalar such that the magnitude of the velocity vector is V=10.

Do you see what you need to do yet?

Hint: What's the modulus of 3i-4j?
I'm not sure what modulus means?
8. (Original post by aznkid66)
The velocity vector is going in the same direction as the directional vector; in other words, the velocity vector is the directional vector 3i-4j multiplied by some scalar such that the magnitude of the velocity vector is V=10.

Do you see what you need to do yet?

Hint: What's the modulus of 3i-4j?
oooh right!! I would rep you but I can't
9. (Original post by physicshelpme)
I'm not sure what modulus means?
Sorry, my bad! It means the same thing as magnitude ^^;
10. (Original post by aznkid66)
Sorry, my bad! It means the same thing as magnitude ^^;
I don't understand, could you please explain how i'd work it out, thank you
11. So a vector is magnitude+direction. The magnitude is the distance of the vector from tip to tail. Simple pythagoras shows that for a vector a=xi+yj the magnitude denoted as |a| is sqrt(x^2+y^2).

Vectors can be used to represent the velocity (speed+direction) of things. In this case, the speed is equal to the magnitude of this velocity vector. Thus, we know the question is asking for a vector with a magnitude of V=10.

If you multiply d=3i-4j by any positive scalar k, then the resultant vector will be going in the same direction as d. So what we're really looking for is a vector kd such that the magnitude |kd|=10.

The trick is to note that, if k is a scalar, |kd|=k|d|, so k|d|=10. Furthermore, since you're given d, you can find |d|=sqrt(3^2 + 4^2)=5. This leads you to k*5=10, and k=2.

So, the answer kd is actually 2d=6i-8j.
12. (Original post by aznkid66)
So a vector is magnitude+direction. The magnitude is the distance of the vector from tip to tail. Simple pythagoras shows that for a vector a=xi+yj the magnitude denoted as |a| is sqrt(x^2+y^2).

Vectors can be used to represent the velocity (speed+direction) of things. In this case, the speed is equal to the magnitude of this velocity vector. Thus, we know the question is asking for a vector with a magnitude of V=10.

If you multiply d=3i-4j by any positive scalar k, then the resultant vector will be going in the same direction as d. So what we're really looking for is a vector kd such that the magnitude |kd|=10.

The trick is to note that, if k is a scalar, |kd|=k|d|, so k|d|=10. Furthermore, since you're given d, you can find |d|=sqrt(3^2 + 4^2)=5. This leads you to k*5=10, and k=2.

So, the answer kd is actually 2d=6i-8j.
thanks alot!

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