# A level physics Circular MOTION PLS HELP

Watch
Announcements
#1
0
3 weeks ago
#2
you have the angular speed, so work out the angle it turns through in 6s
0
#3
(Original post by PizzaMan2989)
you have the angular speed, so work out the angle it turns through in 6s
am not sure what you mean by that, why would you have to find the angle it turns through, i tried to use x=Acos(2pift) but thats obviously not right... am just confused please help am so puzzled, how will I find the angle...
Last edited by dwrfwrw; 3 weeks ago
0
3 weeks ago
#4
so the object is rotating in a circle right? you have the start position and the angle it turns through in a second. You can find the realtive position to p by finding where it is after 6s. Hopefully after that you'll see the answer
0
3 weeks ago
#5
so just multiply 6 by the angular speed
0
#6
(Original post by PizzaMan2989)
so just multiply 6 by the angular speed
still confused, 1st question: why multiply 6 by angular speed(w), as far as am aware theres no formula involving w and t
2nd question: even if I did 6xpi/2 I'd get 3pi/2 which isn't right.
0
3 weeks ago
#7
(Original post by dwrfwrw)
still confused, 1st question: why multiply 6 by angular speed(w), as far as am aware theres no formula involving w and t
2nd question: even if I did 6xpi/2 I'd get 3pi/2 which isn't right.
6 x pi/2 = 3pi that is the ANGLE you have turned through - so where is this on the circle and so what is the displacement?
0
3 weeks ago
#8
(Original post by dwrfwrw)
still confused, 1st question: why multiply 6 by angular speed(w), as far as am aware theres no formula involving w and t
2nd question: even if I did 6xpi/2 I'd get 3pi/2 which isn't right.
(Original post by dwrfwrw)
still confused, 1st question: why multiply 6 by angular speed(w), as far as am aware theres no formula involving w and t
2nd question: even if I did 6xpi/2 I'd get 3pi/2 which isn't right.
(Original post by dwrfwrw)
still confused, 1st question: why multiply 6 by angular speed(w), as far as am aware theres no formula involving w and t
2nd question: even if I did 6xpi/2 I'd get 3pi/2 which isn't right.
ok so the question asks you for the displacement of P after 6s. To find the displacement youre going to need to know where it is on the circle after 6s. The angular velocity tells you where it is on the circle after 1s (pi/2) so on the opposite side to where it started. To find the total angle it turned through, multiply by 6 - Um you should've got 3pi lol. To complete one full revolution, P needs to turn through 2pi, but it turns through 3pi in 6 so there's that extra half turn form the pi left over. So after 6s the particle is on the opposite side. Hopefully now u can find the relative displacement from its start, using the radius given in the question
0
#9
(Original post by PizzaMan2989)
ok so the question asks you for the displacement of P after 6s. To find the displacement youre going to need to know where it is on the circle after 6s. The angular velocity tells you where it is on the circle after 1s (pi/2) so on the opposite side to where it started. To find the total angle it turned through, multiply by 6 - Um you should've got 3pi lol. To complete one full revolution, P needs to turn through 2pi, but it turns through 3pi in 6 so there's that extra half turn form the pi left over. So after 6s the particle is on the opposite side. Hopefully now u can find the relative displacement from its start, using the radius given in the question
uhh i understood what you said but can't the displacement be found using 2pixr=circumference
=2pix(0.8)=8/5 pi
then do I do 8/5 pi / pi from the pi left over to get the displacement?

(Original post by Muttley79)
6 x pi/2 = 3pi that is the ANGLE you have turned through - so where is this on the circle and so what is the displacement?
0
3 weeks ago
#10
(Original post by dwrfwrw)
uhh i understood what you said but can't the displacement be found using 2pixr=circumference
=2pix(0.8)=8/5 pi
then do I do 8/5 pi / pi from the pi left over to get the displacement?
Displacemnet is the straight line distance from where it started.
0
#11
(Original post by Muttley79)
Displacemnet is the straight line distance from where it started.
i know displacement is the radius but I'm still confused, I understood your explanations , wait so do I just do 2pi(1.6) I still don't think that it is right though
0
3 weeks ago
#12
um I haven't really understood what u did? Calculate the circumference and divided by pi?
0
3 weeks ago
#13
(Original post by dwrfwrw)
i know displacement is the radius but I'm still confused, I understood your explanations , wait so do I just do 2pi(1.6) I still don't think that it is right though
Where on the circle is it after 6 seconds? Angle 3pi is where? You then find the straight line [ie no pi] distance.
0
#14
nevermind, is the displacement 1.6? since P is now at -0.8 from 0.8 and doing 0.8--0.8 gives u the straight line distance which is 1.6 thank u guys so much i got really confused as P is in opposite direction from 1.5th of the revolution and displacement is straight line relationship from where it was to where it is thanks for helping me for a 1 marker lol
Last edited by dwrfwrw; 3 weeks ago
0
#15
(Original post by Muttley79)
Where on the circle is it after 6 seconds? Angle 3pi is where? You then find the straight line [ie no pi] distance.
(Original post by dwrfwrw)
nevermind, is the displacement 1.6? since P is now at -0.8 from 0.8 and doing 0.8--0.8 gives u the straight line distance which is 1.6 thank u guys so much i got really confused as P is in opposite direction from 1.5th of the revolution and displacement is straight line relationship from where it was to where it is thanks for helping me for a 1 marker lol
thanks guys for helping me i understand now

(Original post by PizzaMan2989)
um I haven't really understood what u did? Calculate the circumference and divided by pi?
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

Yes, and I've sent off my application! (95)
57.93%
I've made my choices but havent sent my application yet (18)
10.98%
I've got a good idea about the choices I want to make (21)
12.8%
I'm researching but still not sure which universities I want to apply to (12)
7.32%
I haven't started researching yet (9)
5.49%
Something else (let us know in the thread!) (9)
5.49%