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# Quick AQA M1 question watch

1. Hi there,
I am new to TSR so be kind!

A quick question about M1 really:

A Jet Ski is at the origin and is travelling due north at 5ms-1 when it begins to accelerate uniformly. After accelerating for 40 seconds, it is travelling due east at 4ms-1.

c) The Jet Ski is travelling southeast t seconds after it leaves the origin.
i) find t.
ii) find the velocity of the Jet Ski at this time.

I just get confused when the particle is moving southeast, or northeast etc. I can work it out when it is travelling North or East as i=0 or j=0; I am not too sure what to do when it is southeast etc. though.

Any help will be very much appriciated, thank you in advance!
2. Southeast means +ve i and -ve j components. Also the magnitude of the two components are equal, so you're looking at solving an equation of the form y=-x where x is the i component and y is the j component.

Draw a Picture to convince yourself
3. Yeah I get that now!
Thanks very much
4. We need to look at the components of acceleration seperetly.

For the vertical direction.

We use v = u + at to see that:

0 = 5ms^-1 + (a)(40s)
then a = -0.125ms^2

For the horizontol direction

4ms^-1 = 0 + (a)(40s)
then a = 0.1ms^-2

For the jetski to be travelling southeast, the vertical and horizontal componenets of velocity must be equal in magnitude.

Then 5ms^-1 + (-0.125ms^-2)(t) = 0 + (0.1ms^-2)(t)

Here, t = 22.2s

So if we add the initial 40s of travel our answer is 62.2s

Hope this helps.

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