Ho Ho... No

[wyzard]

Can anyone help with these questions please:
1) 8A - How do you find the value of K?
2) With question 10, I integrated but don't know what to do next-hints would be appreciated
I'm thinking when v=0, t=? but I don't know how to find the value of K first
3) With differential equations involving kinematics, is the '+c' still required?

Thank you

Say no more
1) To find k, initially when x is 5m, v is 2m/s. Using this you can find k easily.
2) Set v to zero and solve for t, as velocity is zero when the particle comes to rest.
3) Yes, the C is then found using the initial conditions supplied.

[blacksanta62]

Say no more
1) To find k, initially when x is 5m, v is 2m/s. Using this you can find k easily.
2) Set v to zero and solve for t, as velocity is zero when the particle comes to rest.
3) Yes, the C is then found using the initial conditions supplied.

2) What about 'K', do I just ignore it?
Thanks for the help with the other questions

Edit:
lol, 'K' is in the answer 

[blacksanta62]

Hey, with the attached question:
1) How do I do b)?
2) With c) I can't seem to move forward with my working
dv/dt = 1/1+v
dt/dv = 1+v
t = 1/2(v²) + v + c
v(0) = 0 ===> c = 0
2t = v² + v

Is my working wrong? Is that why I can't move forward?
Thank you

[wyzard]

2) What about 'K', do I just ignore it?
Thanks for the help with the other questions

Edit:
lol, 'K' is in the answer 

k is an unspecified constant, so yeah just ignore it and solve in terms of k

[wyzard]

Hey, with the attached question:
1) How do I do b)?
2) With c) I can't seem to move forward with my working
dv/dt = 1/1+v
dt/dv = 1+v
t = 1/2(v²) + v + c
v(0) = 0 ===> c = 0
2t = v² + v

Is my working wrong? Is that why I can't move forward?
Thank you

For (b), since acceleration is given in terms of x, use the following equation for acceleration:


For (c), to proceed forward, use the quadratic formula as you're solving for v in terms of t.

[blacksanta62]

Thank you Wyzard, the help is appreciated

[blacksanta62]

Probably a fairly simple question (for some) but I can't see how to get the final angle for the attached question. Any help would be appreciated
Also, has anyone started doing exam papers yet? If so, how are you finding the exam 2 papers? Shout out to PB, he's going to full mark!

Edit: I have worked out the first two but need help with how they got 115^o

[zsteve]

115 = 90 + 25, we're taking that as our angle because then cos(115) automatically takes care of the negative sign for the component of force.
Hopefully that makes sense

[blacksanta62]

Thanks for the reply zsteve, could you explain that last part please, don't understand what you mean by it. Thanks