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#1 2005-09-18 23:29:46
- Jaswahhihi
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Mechanics 2!!
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
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#2 2005-09-19 02:57:34
- kylekatarn
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Re: Mechanics 2!!
should we consider
or
Last edited by kylekatarn (2005-09-19 03:04:06)
#3 2005-09-19 03:18:13
- kylekatarn
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Re: Mechanics 2!!
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 below horizontal
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 (2005-09-19 04:16:41)
#4 2005-09-19 03:57:44
- Jaswahhihi
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Re: Mechanics 2!!
Sorry mate, while I was waiting for a reply I worked it out. And its just 9.8. Thanks though 
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#5 2005-09-19 04:16:15
- kylekatarn
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Re: Mechanics 2!!
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!