# circular motion

Watch
Announcements
Thread starter 1 month ago
#1
I do not know how to do part a of this question, any guidance would be greatly appreciated. Thanks.
0
Thread starter 1 month ago
#2
0
1 month ago
#3
(Original post by RLangdon569)
Since you're dealing with a reaction on the wire and circular motion, that would suggest using formula for force to move in a circle.

You're going to need the velocity, when at an angle theta, so conservation of energy to get it in terms of the initial velocity.

And you're told that the initial veloicty is just sufficient to carry it to the top of the wire, so you can form an equation for the initial velocity.

Put it all together; lots of cancellation and you have theta. (Does work!)
Last edited by ghostwalker; 1 month ago
0
Thread starter 1 month ago
#4
(Original post by ghostwalker)
Since you're dealing with a reaction on the wire and circular motion, that would suggest using formula for force to move in a circle.

You're going to need the velocity, when at an angle theta, so conservation of energy to get it in terms of the initial velocity.

And you're told that the initial veloicty is just sufficient to carry it to the top of the wire, so you can form an equation for the initial velocity.

Put it all together; lots of cancellation and you have theta. (Does work!)
Hi, thank you for the outline. Sorry if I am being obtuse but I calculated that initial velocity is sqrt(4ag). The equation for force would be T-mgcosTheta= maw^2 . Using conservation of energy, v = sqrt ( 2ag(2-costheta)). Not quite sure how to put this together. thanks
0
1 month ago
#5
(Original post by RLangdon569)
Hi, thank you for the outline. Sorry if I am being obtuse but I calculated that initial velocity is sqrt(4ag). The equation for force would be T-mgcosTheta= maw^2 . Using conservation of energy, v = sqrt ( 2ag(2-costheta)). Not quite sure how to put this together. thanks
In order:

I'd leave the initial velocity, u, as u^2 since you're using it in the KE of the conservation of energy equation.

You're told what T is in the question.

For force to move in a circle, I'd use rather than since we're getting velocity from the conservation of energy.

Again I'd leave v as v^2, for the same reason as for u, though your equation for v doesn't look correct - check the derivation.
0
Thread starter 1 month ago
#6
(Original post by ghostwalker)
In order:

I'd leave the initial velocity, u, as u^2 since you're using it in the KE of the conservation of energy equation.

You're told what T is in the question.

For force to move in a circle, I'd use rather than since we're getting velocity from the conservation of energy.

Again I'd leave v as v^2, for the same reason as for u, though your equation for v doesn't look correct - check the derivation.
Is this correct ?
0
1 month ago
#7
(Original post by RLangdon569)
Is this correct ?
4 lines from the bottom is correct.

@ 3 lines from the bottom you've gone wrong.
0
Thread starter 1 month ago
#8
(Original post by ghostwalker)
4 lines from the bottom is correct.

@ 3 lines from the bottom you've gone wrong.
I see it now, silly mistake. 3costheta = 3/2, theta = Pi/3
0
1 month ago
#9
(Original post by RLangdon569)
I see it now, silly mistake. 3costheta = 3/2, theta = Pi/3
Agreed.
0
Thread starter 1 month ago
#10
(Original post by ghostwalker)
Agreed.
sorry to be a pain, but I assumed for part ii that I would be using the relationship v=rw , however that doesn't seem to work out.
0
Thread starter 1 month ago
#11
(Original post by ghostwalker)
Agreed.
Appreciate the guidance and help you give sincerely.
0
1 month ago
#12
(Original post by RLangdon569)
sorry to be a pain, but I assumed for part ii that I would be using the relationship v=rw , however that doesn't seem to work out.
Seems fine to me. Post working/thoughts.
0
Thread starter 1 month ago
#13
(Original post by ghostwalker)
Seems fine to me. Post working/thoughts.
k=2 ?
0
1 month ago
#14
(Original post by RLangdon569)
k=2 ?
Yes.
0
Thread starter 1 month ago
#15
(Original post by ghostwalker)
Yes.
Is part iii a case of v^2 =u^2 + 2as ?
0
Thread starter 1 month ago
#16
(Original post by ghostwalker)
Yes.
0
1 month ago
#17
(Original post by RLangdon569)
Is part iii a case of v^2 =u^2 + 2as ?
Is acceleration constant in this scenario?
0
Thread starter 1 month ago
#18
(Original post by ghostwalker)
Is acceleration constant in this scenario?
No
0
Thread starter 1 month ago
#19
(Original post by ghostwalker)
Is acceleration constant in this scenario?
Would you please offer your guidance how to go about part iii ? Thanks a lot
0
1 month ago
#20
(Original post by RLangdon569)
No
So, suvat doesn't apply. How else might you get the angular acceleration?
0
X

new posts
Back
to top
Latest
My Feed

### Oops, nobody has postedin the last few hours.

Why not re-start the conversation?

see more

### See more of what you like onThe Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

### Poll

Join the discussion

#### What factors affect your mental health the most right now?

Anxiousness about lockdown easing (166)
4.89%
Uncertainty around my education (498)
14.68%
Uncertainty around my future career prospects (379)
11.17%
Lack of purpose or motivation (473)
13.94%
Lack of support system (eg. teachers, counsellors, delays in care) (164)
4.83%
Impact of lockdown on physical health (208)
6.13%
Loneliness (288)
8.49%
Financial worries (122)
3.6%
Concern about myself or my loves ones getting/having been ill (137)
4.04%
Exposure to negative news/social media (155)
4.57%
Lack of real life entertainment (186)
5.48%
Lack of confidence in making big life decisions (302)
8.9%
Worry about missed opportunities during the pandemic (315)
9.28%