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## Topic review (newest first)

kylekatarn
2005-09-19 04:16:15

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!

Jaswahhihi
2005-09-19 03:57:44

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

kylekatarn
2005-09-19 03:18:13

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!

kylekatarn
2005-09-19 02:57:34

should we consider

or

Jaswahhihi
2005-09-18 23:29:46

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