Emath
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Hi, im really stuck on an isaac physics question and was wondering if anyone could help
its called "running return" and im stuck on part D.
thankyou!

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Eimmanuel
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(Original post by Emath)
Hi, im really stuck on an isaac physics question and was wondering if anyone could help
its called "running return" and im stuck on part D.
thankyou!

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What have you attempted?
Even your working is wrong, it can still give us some clues about your understanding.

It is always better to provide a link to the problem instead of taking a picture using your phone.
If you want to take a picture, you can take a look at the posting guidelines of how to take pictures.
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Emath
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ah okay haha, sorry I didn't realise. here's the link: https://isaacphysics.org/questions/running_return

I've managed to work out the first 3 parts but the last one just confuses me.

I have worked out the time it takes the ball to get from A to B as 1.132.... seconds. And I thought that, because the runner turns around as soon as the ball leaves A, that the Initial velocity would be 0m/s, the acceleration would be 6.9m/s² and the time it would take them would be 1.132... s. but using SUVATs I got the wrong distance for it
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Eimmanuel
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(Original post by Emath)
ah okay haha, sorry I didn't realise. here's the link: https://isaacphysics.org/questions/running_return

I've managed to work out the first 3 parts but the last one just confuses me.

I have worked out the time it takes the ball to get from A to B as 1.132.... seconds. And I thought that, because the runner turns around as soon as the ball leaves A, that the Initial velocity would be 0m/s, the acceleration would be 6.9m/s² and the time it would take them would be 1.132... s. but using SUVATs I got the wrong distance for it
How do you use SUVAT equations?

There is a graph in the following thread that may help.
https://www.thestudentroom.co.uk/sho...php?p=87284146
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Emath
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(Original post by Eimmanuel)
How do you use SUVAT equations?

There is a graph in the following thread that may help.
https://www.thestudentroom.co.uk/sho...php?p=87284146
Ah that graph helped a lot thankyou! I was originally doing the same thing as the other person with the SUVATS.

I got the area under OMN as 6.9t^2 and the area under NQ as [(-6.9 delta t^2 +13.8 t delta t - 6.9t^2)/2) and then added them together. And with delta t as 1.32... the quadratic I ended up with is [6.9t^2 + 15.63 t - 8.8477 = 0 ] - I solved this to get t= 0.469 or t= -2.734. But I know this is wrong because by working out the area of half OMN (using the positive value of t) you get the maximum displacement as 0.7589 which isn't right. Do you know where I'm going wrong?
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Eimmanuel
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(Original post by Emath)
Ah that graph helped a lot thankyou! I was originally doing the same thing as the other person with the SUVATS.

I got the area under OMN as 6.9t^2 and the area under NQ as [(-6.9 delta t^2 +13.8 t delta t - 6.9t^2)/2) and then added them together. And with delta t as 1.32... the quadratic I ended up with is [6.9t^2 + 15.63 t - 8.8477 = 0 ] - I solved this to get t= 0.469 or t= -2.734. But I know this is wrong because by working out the area of half OMN (using the positive value of t) you get the maximum displacement as 0.7589 which isn't right. Do you know where I'm going wrong?
It is also good to state your starting equation (or expression) instead of the final equation (expression). The starting equation (or expression) is usually similar.
In the other thread at post #10, I raised a question. The answer to that question is the key to part D.
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Emath
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Just as I was typing my response, I realised that I had worked out the area of the second triangle wrong and now I know what I did wrong haha. But I managed to get the right answer as 1.5m (I had a few rounding issues with Isaac physics though lol). But thankyou so much - I appreciate all the help!
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Eimmanuel
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(Original post by Emath)
Just as I was typing my response, I realised that I had worked out the area of the second triangle wrong and now I know what I did wrong haha. But I managed to get the right answer as 1.5m (I had a few rounding issues with Isaac physics though lol). But thankyou so much - I appreciate all the help!
Good to hear that.
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