# Maths A level projectile question help!

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I'm stuck on part 1. of the question. I looked at the mark scheme and it says the initial velocity is P. I am a bit confused as to why it is not Pcosα. Please could someone help me understand this question.

Last edited by username4506446; 1 year ago

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#2

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I'm stuck on part 1. of the question. I looked at the mark scheme and it says the initial velocity is P. I am a bit confused as to why it is not Pcosα. Please could someone help me understand this question.

**Anonymous_4657**)I'm stuck on part 1. of the question. I looked at the mark scheme and it says the initial velocity is P. I am a bit confused as to why it is not Pcosα. Please could someone help me understand this question.

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Since its a vector, you don't need to apply sin or cos when resolving the forces

**ApexCoder**)Since its a vector, you don't need to apply sin or cos when resolving the forces

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#5

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Thanks. How come? it it just a rule that I have got to learn?

**Anonymous_4657**)Thanks. How come? it it just a rule that I have got to learn?

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Answer this question for me, why do you use sin or cos in the first place

**ApexCoder**)Answer this question for me, why do you use sin or cos in the first place

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#7

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Don’t you draw a triangle and resolve forces? Maybe I’m wrong

**Anonymous_4657**)Don’t you draw a triangle and resolve forces? Maybe I’m wrong

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#8

You are resolving vertically and you are already given a vertical magnitude of the velocity (or the vertical component of the velocity) by the j-component of the velocity vector.

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Sometimes for a vector (a force, a velocity, impulse etc.), the direction of it given to you may not be acting along the direction you are resolving in.

This is why when finding a vector's effect (in the direction you are resolving in), you have to use sin or cos.

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Sometimes for a vector (a force, a velocity, impulse etc.), the direction of it given to you may not be acting along the direction you are resolving in.

This is why when finding a vector's effect (in the direction you are resolving in), you have to use sin or cos.

Last edited by simon0; 1 year ago

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it it just a rule that I have got to learn?

**Anonymous_4657**)it it just a rule that I have got to learn?

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