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**Jaswahhihi****Member**- Registered: 2005-07-23
- Posts: 11

darn I hate this question! Theres no diagram but Ill copy the question out. Oh and the topics Parbolic motion.

A particle is projected at a speed of 45ms at an angle of 30 degrees above the horizontal.

(a) Calculate

(i) the speed and direction of the motion of the particle after 4 seconds,

(ii) the maximum height above the point of projection reached by the particle.

I can do (b) but the first two are the ones that got me. Anyhoo the answers are:

(a)

(i) 42.4 ms at 23.2 degrees below the horizontal

(ii) 25.8 m

98% of the teenage population does or has tried smoking pot. If you're one of the 2% who hasn't, copy & paste this into your signature.

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**kylekatarn****Member**- Registered: 2005-07-24
- Posts: 445

should we consider

or

*Last edited by kylekatarn (2005-09-18 05:04:06)*

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**kylekatarn****Member**- Registered: 2005-07-24
- Posts: 445

consider the gravity constant **g = - 9.81**

*Initial conditions (t = 0 s) *

lets find the initial speed components vx and vy

i) Speed and Angle @ t=4s

the x component doesn't change

the y component changes because of gravity

Speed is a vector, not a scalar.

You probably want the norm...

Now finding the angle is easy.:

θ = -23.2º means 23.2º

ii) Finding the maximum height

we need to find the time corresponding to that moment -

since:

and

plug this value in the y(t) equation and find the max height.

And that's it!

*Last edited by kylekatarn (2005-09-18 06:16:41)*

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**Jaswahhihi****Member**- Registered: 2005-07-23
- Posts: 11

Sorry mate, while I was waiting for a reply I worked it out. And its just 9.8. Thanks though

98% of the teenage population does or has tried smoking pot. If you're one of the 2% who hasn't, copy & paste this into your signature.

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**kylekatarn****Member**- Registered: 2005-07-24
- Posts: 445

lol. I was working on the solution so I left the post open for a while...

I must type faster next time : ) Writing the solution in latex takes longer than actually solving it. lolol

Anyway, it was great to work on physics again!

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