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# M1 - speed with 2 velocities/acceleration watch

1. hi there
im just wondering how i would go about finding the speed when i have 2 velocities and acceleration
i know speed = displacment/time and displacment = velocity x time but i have 2 different velocities.
for example:
i am given the initial velocity = 2i
i am given the acceleration = i
i worked out the end velocity = 5i
time = 3 seconds

i have tried a few different ways but none give me the right answer
and i can't find an example similar in the book

any help is much appreciated
2. What's the full question? I'm not sure what you need to find.

Are you talking about relative velocities?
3. "a particle P has velocity u initially and acceleration a. Find the velocity and the speed after t seconds when:
u = 2i, a = i, t = 3"

and ive found the velocity for all of them (this one is 5i)
4. Well, it's initial velocity is 2i, after another 3 seconds accelerating at i, then the final velocity will be 5i yes.

Velocity is a vector btw, while speed is a scalar.

So, while the velocity is 5i (magnitude and direction) the speed is simply 5.
5. hi there
one question though, why would the speed not be 5/3 given that it gives you the time to be 3 seconds? sorry if this is an obvious answer
6. (Original post by confusedmathsguy)
hi there
one question though, why would the speed not be 5/3 given that it gives you the time to be 3 seconds? sorry if this is an obvious answer
speed is the magnitude of velocity.... just the '5' bit of '5i'

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