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# Physics Projectiles question

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Why bother with a post grad course - waste of time? 17-10-2016
1. Hi

I;ve been trying to work out this question for about an hour and can't seem to get it right. I know the answer is C because I've checked the answers but can't seem to work out how to get to it and I really want to know.

Its question number 2 on the picture

Matt
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2. I'm guessing you assumed he fired the arrow at an angle? If you assume he fires it vertically upwards (I guess because they normally make it clear if the object was fired/thrown or whatever at an angle) then you get the correct answer. Using v^2=u^2+2as with v=0, u=30 (you don't care about horizontal velocity since the arrow was fired vertically upwards), a=9.81 and s=? (remembering to add 1 to your value of s since it was fired from 1 metre above the ground).
3. (Original post by victoria98)
I'm guessing you assumed he fired the arrow at an angle? If you assume he fires it vertically upwards (I guess because they normally make it clear if the object was fired/thrown or whatever at an angle) then you get the correct answer. Using v^2=u^2+2as with v=0, u=30 (you don't care about horizontal velocity since the arrow was fired vertically upwards), a=9.81 and s=? (remembering to add 1 to your value of s since it was fired from 1 metre above the ground).
It's not that you're supposed to assume he fires it vertically. In the question he does fire it at an angle clearly because it has both horizontal and vertical components.

The point of the question is to recognise that you only consider the vertical component and hence do a simple suvat calculation, adding 1m at the end
4. (Original post by Student403)
It's not that you're supposed to assume he fires it vertically. In the question he does fire it at an angle clearly because it has both horizontal and vertical components.

The point of the question is to recognise that you only consider the vertical component and hence do a simple suvat calculation, adding 1m at the end
Ah yes that's right, my bad. That does make more sense. Either way the calculation is the same
5. (Original post by victoria98)
Ah yes that's right, my bad. That does make more sense. Either way the calculation is the same
Indeed the calculation is the same But the problem arises when people wrongly think they have the right understanding, and then get confused in other questions or the exam because they applied this misconception

Anyway that was just rambling
6. (Original post by Student403)
Indeed the calculation is the same But the problem arises when people wrongly think they have the right understanding, and then get confused in other questions or the exam because they applied this misconception

Anyway that was just rambling
I do get what you mean, and I remember I used to 'understand' projectile motion for G481 and then immediately after, I forgot most of the stuff (evidently) but I did get the marks on the question that came up in my exam. Should probably make sure I'm 100% sure on what I'm doing before I pass it on to someone else though.
7. (Original post by victoria98)
I do get what you mean, and I remember I used to 'understand' projectile motion for G481 and then immediately after, I forgot most of the stuff (evidently) but I did get the marks on the question that came up in my exam. Should probably make sure I'm 100% sure on what I'm doing before I pass it on to someone also though.
It will come with practice
8. (Original post by Student403)
It will come with practice
It's a good thing I only need an A for my firm choice (and projectile motion in A2 is not very common haha)
9. (Original post by victoria98)
It's a good thing I only need an A for my firm choice (and projectile motion in A2 is not very common haha)
Haha true
10. Thanks guys victoria98 and Student403 I've got the answer now. I think I was looking too deeply into it

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