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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


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.

#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 = -23.2 means 23.2 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 smile


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.

#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 smile

Anyway, it was great to work on physics again!

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