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# M1 Suvat question June 2005 question 4

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1. Hey.
I know for this question i need to get 2 different suvat equations then sole simultaneously but i cant find where i have made a mistake.
Attachment 518163518165
Thanks.
Attached Images

2. (Original post by SamuelN98)
Hey.
I know for this question i need to get 2 different suvat equations then sole simultaneously but i cant find where i have made a mistake.
Attachment 518163518165
Thanks.
For 'the next 1.2m', the initial velocity is not 'u' anymore since the particle has already been travelling for 0.8s and must have changed speed.

Instead, use the fact that P has travelled 8m in 2s with initial velocity 'u'.
3. (Original post by SamuelN98)
Hey.
I know for this question i need to get 2 different suvat equations then sole simultaneously but i cant find where i have made a mistake.
Attachment 518163518165
Thanks.
For the second bit of the motion, you seem to have said let but this is not true, you are considering motion in the last 6 metres, hence the initial speed is .

Urgh, nevermind. Ninja-ed.

4. Attachment 518171518173
I have another question...
I don`t understand why i cant use v=u+at for question (iii).
Attached Images

5. (Original post by SamuelN98)
I don`t understand why i cant use v=u+at for question (iii).
That's a kinematics question, you need to use calculus.

SUVAT equations are derived under the assumption that acceleration is constant. In this case, acceleration (and velocity) varies as a function of time, so you need to throw all thoughts of SUVAT out of your head when looking at those questions and focus on using calculus. You know how to maximise functions (*coughs* derivative) and you're given velocity as a function of time, so...
6. (Original post by SamuelN98)

Attachment 518171518173
I have another question...
I don`t understand why i cant use v=u+at for question (iii).
Because Q's acceleration isn't constant. You need to differentiate the velocity expression to get an expression for the acceleration at time t.

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