Basic M1 Vectors Question

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I can't seem to understand what's going on in the example above! Can someone please explain to me what is going on and why?

speed is 15, so you need a velocity vector with a magnitude of 15

the direction of your vector has to be parallel to 3i-4j

so you need a multiple of 3i-4j that has a magnitude of 15



I assume that you know the magnitude of 3i-4j is 5

so you multiply it by 3 to get a magnitude of 15



once you have your velocity vector, you do that twice because you have 2 seconds

you know the direction of the velocity & its magnitude, so you can work out the correct components of velocity.

thanks!

by the way, would you mind seeing where I went wrong in my working out? I found in part a of the question so I thought I could use that v and substitute it into the equation r = r0 + vt but I didn't get the right answer(I'm referring to part B)!

in red is for zero acceleration... you need

r = r_o + ut + 0.5at²

Oh okay, so if the particle is accelerating I must use "long formula" but if it isn't accelerating then I should use r=r0 + Vt?

yes... it is exactly the same formula but with a = 0

Thank you soo much, you explained that perfectly! 😄😊😀😃

no worries blud

Do do you mind spotting where I went wrong in question 5, part a? 😨

your triangle of forces... the big angle on the left should be 90 degrees, the top one 40...

it is like making a jigsaw from the 3 lines on the diagram. you move them around, do not change the direction until they fit nose to tail. then the angles in the triangle can be read off from the angles in the original diagram.