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# M1 Kinematics Question watch

1. I'm stuck on this question:

Two balls are projected simultaneously from two points A and B. The point A is 54m vertically below B. Initially one ball is projected from A towards B with speed 15ms^-1. At the same time, the other ball is projected from B with speed 12ms^-1.

Find the distance between A and the point where the balls collide.

For A, I have:
S=s
U=15
V=
A=-9.8
T=t

For B:
S=s-54
U=12
V=
A= 9.8
T=t

For A,
S=15t-4.9t^2

For B,
S=12t+4.9t^2+54

So, 9.8t^2-3t+54 which I can't find a root for.

Thanks for any help.
2. Bump
3. for the purposes of your calculation you have made the downwards vectors positive and the upwards vectors negative, yes?

the acceleration for both should be 9.8 then, as gravity is acting as a downwards force on both.

your initial velocity for B now should be -12, as the ball is moving upwards.

this may be a bit easier to conceptualize if you make the upwards vectors positive and the downwards negative, using -9.8 as the acceleration for both, -15 as the initial velocity for A and 12 for B.
4. You morons M1 is a Motorway, what has it got to do with Maths brah

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Updated: November 5, 2015
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