[thewait]

This questions is really pissing me off as i can't do them.

6. A particle moves from the point A with vector ( 3i + 4j ) metres
to the point B with position vector ( 120i - 110j ) metres in 10 seconds,
moving with constant acceleration.
The particle had velocity (i - j) ms-1 at A.
(a) Determine the distance between the two points.
(b) Determine the average velocity of the particle.
(c) Calculate the acceleration of the particle.
(d) Calculate the velocity of the particle at B

a) i tried using suvat but that never worked out, then i tried taking the vectors away but that also failed aswell.
b) am guessing i need to use the formula Average Velocity=total distance/total time?
c)suvat? but don't know whats my u,v etc
d)No idea.

P.s As you can see i need a big help on vectors and my book is useless in this so if anybody got a revision website it'll be greatly appreciated.

[Nfixlol]

u = (i - j) m/s
s = [(120i-110j) - (3i + 4j)] metres
t = 10 sec

for (a), you just need to subtract A's position vector from B's position vector.
for (b), use the answer you got in part (a), divided by t, i.e. average velocity = displacement/time
(c), s = ut + 0.5at² -> s = 10(i-j) + 100(0.5a) and solve for a.
for (d), use v² = 2as + u² now that you have a value for a.

edit: my bad, good catch . fixed, changed distance to displacement.

[generalebriety]

a) The displacement travelled is s = 117i - 114j. If you draw yourself a diagram, you'll see that to work out how long this vector is you need to use Pythagoras.

b) Yes, you can use average velocity = displacement / time (not distance, because we're working with vectors here!). Here's another way: the acceleration is constant, so let's use suvat. The displacement travelled is s = 117i - 114j (by subtracting), the time taken is t = 10, the starting velocity is u = i - j. From this you can work out the final velocity v. Then, again because the acceleration is constant, the average velocity is (u+v)/2.

c) As above.

d) As above.

[thewait]

Originally Posted by generalebriety

a) The displacement travelled is s = 117i - 114j. If you draw yourself a diagram, you'll see that to work out how long this vector is you need to use Pythagoras.

b) Yes, you can use average velocity = displacement / time (not distance, because we're working with vectors here!). Here's another way: the acceleration is constant, so let's use suvat. The displacement travelled is s = 117i - 114j (by subtracting), the time taken is t = 10, the starting velocity is u = i - j. From this you can work out the final velocity v. Then, again because the acceleration is constant, the average velocity is (u+v)/2.

c) As above.

d) As above.

Thanks for that. Got the answers.

And Nfixlol thanks aswell

[thewait]

Originally Posted by generalebriety

a) The displacement travelled is s = 117i - 114j. If you draw yourself a diagram, you'll see that to work out how long this vector is you need to use Pythagoras.

b) Yes, you can use average velocity = displacement / time (not distance, because we're working with vectors here!). Here's another way: the acceleration is constant, so let's use suvat. The displacement travelled is s = 117i - 114j (by subtracting), the time taken is t = 10, the starting velocity is u = i - j. From this you can work out the final velocity v. Then, again because the acceleration is constant, the average velocity is (u+v)/2.

c) As above.

d) As above.

Am still not getting part b) right. Got my answer as 16.336 but thats wrong. I did my answer for a) /10.

[generalebriety]

Originally Posted by thewait

Am still not getting part b) right. Got my answer as 16.336 but thats wrong. I did my answer for a) /10.

I think you're misunderstanding what the question is asking for. The question has asked you for the velocity, which is a vector, whereas you've given the speed, a scalar. The velocity of an object is the vector in the direction of its motion with size equal to its speed (in the same way that the displacement of an object is the vector pointing in the direction it's travelled with size equal to the distance it's travelled).

Notice that average speed = distance / time, average velocity = displacement / time.

[thewait]

Originally Posted by generalebriety

I think you're misunderstanding what the question is asking for. The question has asked you for the velocity, which is a vector, whereas you've given the speed, a scalar. The velocity of an object is the vector in the direction of its motion with size equal to its speed (in the same way that the displacement of an object is the vector pointing in the direction it's travelled with size equal to the distance it's travelled).

Notice that average speed = distance / time, average velocity = displacement / time.

ohhhh so i just do the displacement (117i-114j)/10 then. Feel like an idiot lol thanks for the help once again.

[Economic Historian 1]

which exam board are you with? I thought all M1's were already done...

[thewait]

Originally Posted by Economic Historian 1

which exam board are you with? I thought all M1's were already done...

AQA is june 5th.

[Economic Historian 1]

Originally Posted by thewait

AQA is june 5th.

ah, i see. Well, good luck then

[thewait]

Originally Posted by Economic Historian 1

ah, i see. Well, good luck then

Cheers man.