Calling all Physics People, help!

[kevinthenerd]

I always think about cosines and sines intuitively. Imagine if the angle was zero. Would the number that you're multiplying by be zero or one? If it's zero, use sine. If it's one, use sine. In this case, if the angle from the horizontal was zero, you'd get the full brunt of the accerlation in the horizontal direction. If it was 90 degrees, you wouldn't get any. That's why I chose cosine.

 

[dighn]

wow this thread sure got a lot of replies unlike some of the other ones

 

[Triumph]

Did you get it yet or not? This really isn't that hard.

 

[DrPizza]

Originally posted by: dullard

Originally posted by: DrPizza
p.s. I'm a physics and calculus teacher.... I'd go with my solution, rather than dullard's 🙂

We always seem to post in the same threads. Now was that a joke (hence the smiley) or did I do something stupid that I cannot see?

Sorry dullard! I only glanced up at the posters.... Your solution is the same as mine.... I had just read evadman's before I posted... but then I did the 2nd reply and looked up and caught your name on accident. 🙂

 

[her209]

Originally posted by: johnjohn320

Originally posted by: her209
d=s0+v0t+.5at^2

50=0+0+.5(4)t^2

100 = 4t^2

25 = t^2

t=5

deriving d by t, we get

d/t=v=v0+at

v=0+4*5=20

so the car is moving 20 m/s when it hits the end of the incline

you then need to use the sin rule to find the horizontal & vertical velocity component

vx = 20 sin (90-24) ~ 18.27 m/s
vy = 20 cos (90-24) ~ 8.13 m/s

Next you need to figure out how long it will take for the car to drop 30 m starting at the initial velocity of 8.13 m/s. (Part B)

Then you can take that time and plug it into the d=vxt eq to figure out how far away it is from the edge of the cliff. (Part A)

Ok, I think that was the part I was missing. Had never seen those functions before. OK, I think I might have it now, thanks!

I think its:

sin (theta) = opposite / hypotenuse

cos (theta) = adjacent / hypotenuse

tan (theta) = sin (theta) / cos (theta) = opposite / adjacent

 

[johnjohn320]

Originally posted by: Triumph
Did you get it yet or not? This really isn't that hard.

Yes I've got it now. There's always at least one of you people, "c'mon, stupid, why don't you get this? This is easy!"

My teacher never went over the trig stuff, I swear it. That's really the only reason I had a hard time with this.

Thanks for the help guys! 😀

 

[Rayden]

if he doesn't go over it in the next class then something's wrong, or someone was napping.
ask him.

 

[Ausm]

Originally posted by: Brutuskend
click me

looks like one of my Calc finals 😉

Ausm

 

[johnjohn320]

Originally posted by: Rayden
if he doesn't go over it in the next class then something's wrong, or someone was napping.
ask him.

will do.

 

[MikeMike]

page 73, number 21. goes onto page 74 also

muhahaha. you coulda looked in the back of the book to find the answer and then worked backwards.


Serway & faughn are the authors.

MIKE

 

[MikeMike]

bah that question wasnt too hard.

MIKE

 

[johnjohn320]

Originally posted by: nourdmrolNMT1
bah that question wasnt too hard.

MIKE

Yes I've got it now. There's always at least one of you people, "c'mon, stupid, why don't you get this? This is easy!" My teacher never went over the trig stuff, I swear it. That's really the only reason I had a hard time with this.

Thanks for the help guys!