Titled reference frame, N2L with position and velocity

learningphysics

cool. plugging that into dx should work.

Oblio

dx = vocos(theta)vosin(theta)/(1/2)gcos(phi) - (1/2)gsin(phi)vosin(theta)/(1/2)gcos(phi)

learningphysics

you missed t^2... didn't square t.

Oblio

oops.
man im bad..

Oblio

dx = vocos(theta)vosin(theta)/(1/2)gcos(phi) - (1/2)gsin(phi)(vosin(theta)/(1/2)gcos(phi))^2

on the right side i can cancel out the (1/2) on the bottom and top, as well as the g, giving,

dx = vocos(theta)vosin(theta)/(1/2)gcos(phi) - sin(phi)(vosin(theta)/cos(phi))^2

learningphysics

careful the 1/2 and g are squared...

Oblio

oops again.

so im left with
dx = vocos(theta)vosin(theta)/(1/2)gcos(phi) - sin(phi)(vo^2 sin(theta) ^2 / (1/2) g (cos(phi)^2)

learningphysics

Looks good... try to simplify and use a trig identity to get it to look like the formula they gave for the range...

Oblio

will trig identities apply since theta and phi are present?

Oblio

im confused how one would ever get, for example : cos (theta + phi) through simplifying

learningphysics

try a little factoring of your equation also... look up the identity for cos(A+B)...

Oblio

i found that cos (a+b) = cosacosb +/- sinasinb... but i dont have that relationship anywhere

learningphysics

first write everything over 1 denominator... then compare what you have to the formula you need to get... a little factoring will give you the answer.

Oblio

k im at
dx= vo^2sin(theta)*(cos(theta)-sin(phi)) / (1/2)cos(phi)^2(sin(theta))

learningphysics

factoring out the sin(theta) was correct... but you made a mistake somewhere...

Oblio

i cant factor out a vo^2?

learningphysics

yes you can... I was referring to the sin's cos's... check your work... your denominator should only have [cos(phi)]^2