Help Please with Resisted Motion Q (1 Viewer)

[mreditor16]

Okay here it is: thanks in advance....

http://postimg.org/image/no9y9kf6v

And please just give me the complete answer, not just a hint, because I tried it a lot and am not dumb.

Thanks!

 

[Immortality]

Draw a nice force diagram an try again (Y)

 

[mreditor16]

Immortality, it was in 4U HW from Cambridge, you done it? haha

 

[Immortality]

If it helps, did you remember to add the distance of free fall?

 

[mreditor16]

of course, but I get ln(g/2) in my answer and it doesn't cancel out. have you done it, immortality, and if you not, can you do it?

and then photo it or latex it?

come on immortality. you know you want to.

 

[Immortality]

There are two terms with ln(g/some random number) subtracting each other, thus cancelling out the g's to get something like ln(1/2) which is -ln2

And pls. Im sure you can get it out, giving the solutions to you will be too generous.

 

[Kurosaki]

I tried doing this question, but can't seem to get the 8 >___<. Must've missed something...
@ mreditor what exercise is this in 4U Cambridge (I presume Arnold and Arnold)?

 

[mreditor16]

I tried doing this question, but can't seem to get the 8 >___<. Must've missed something...
@ mreditor what exercise is this in 4U Cambridge (I presume Arnold and Arnold)?

yep Arnold and Arnold. Ex 7.2 Q3.

btw I replied to your pm.

 

[mreditor16]

There are two terms with ln(g/some random number) subtracting each other, thus cancelling out the g's to get something like ln(1/2) which is -ln2

And pls. Im sure you can get it out, giving the solutions to you will be too generous.

its not coming out. send me!!!!!!!!!!!!!!!!!1

 

[Kurosaki]

Got it. I derped hard haha
@ mreditor the question requires that for the initial part of the fall (before the parachute is released) we assume it is falling purely under the influence of gravity, did you know that?

 

[mreditor16]

yep yep got that. go on..

 

[Immortality]

As i was saying, you must consider the freefall as well

 

[Kurosaki]

initially before the parachute opens.
Integrating, (initially the person would have 0 velocity)

Integrating v wrt t to get the distance fallen during free fall, letting x be the distance fallen,



When the parachute is open,

Therefore,


Let y be the distance fallen from the point where the parachute opened. Integrating the following mess, we get the distance fallen when the parachute is opened. Add the distances and you should be done =)

 

[mreditor16]

As i was saying, you must consider the freefall as well

i know, i did. i broke it up into 2 stages.....

just put up thesolution. argh!!

 

[mreditor16]

THANKS SO MUCH KUROSAKI. I'll look through it and get back to you guys! Thanks again.

 

[Fade1233]

initially before the parachute opens.
Integrating, (initially the person would have 0 velocity)

Integrating v wrt t to get the distance fallen during free fall, letting x be the distance fallen,



When the parachute is open,

Therefore,


Let y be the distance fallen from the point where the parachute opened. Integrating the following mess, we get the distance fallen when the parachute is opened. Add the distances and you should be done =)

Precisely.

 

[mreditor16]

omg i realied what i did wrong - i fked up adding ln( ... ) - ln{....}

soz guys for the trouble and thanks again!