Mechanics: Resolving forces and N2L

OP

rbnphlp

what did you get when you resolved your forces?

Something horribly wrong! I think I'm making a very basic error but I can't see it :s-smilie:

I tried resolving and got:
(Where T1=tension in AC and T2 tension in AB)

T1sin30 - T2sin30= 450 x 0.5 (Using F=ma) :s-smilie:

Reply 3

bob9001

T1sin30 - T2sin30= 450 x 0.5 (Using F=ma) :s-smilie:

Because you T_1sin30 is the vertical component ... Remember there is accleration only in the horizontal direction i.e

T_2cos30-T_1cos30=ma

Reply 4

OP

rbnphlp

Because you T_1sin30 is the vertical component ... Remember there is accleration only in the horizontal direction i.e

T_2cos30-T_1cos30=ma

Sorry yeah I actually meant cos lol

where do I go from here:

T_2cos30-T_1cos30=225

?

Reply 5

steve2005

17

bob9001

Hey guys

I'm a little stuck on a question! It's very fustrating as it looks very simple :s-smilie:

:

Two cables, AB and AC are attached to a cable car as shown in the diagram attached. The cable car has mass 450kg.
The cable car travels horizontally in the direction --->. Model the cable car as a particle and assume no air resistance is present. As the car moves the angles shown do not change. Find the tension in each cable when a=

0.5 m/s^2.

I've tried to resolve it in the x direction since acceleration is in the x direction and use F=ma but I'm not getting the right answer. Anyone help? :smile:

I get 2335N and 2075N am I correct ?

Reply 6

bob9001

Sorry yeah I actually meant cos lol

where do I go from here:

T_2cos30-T_1cos30=225

?

you now need the vertical components..

Spoiler

Reply 7

OP

steve2005

I get 2335N and 2075N am I correct ?

Nope sorry

Reply 8

OP

rbnphlp

you now need the vertical components..

Spoiler

Ahhhh yes! This is what I was doing but was confused about the 2 equations I got!

You can't add/subtract them can you?
Can you divide so sin/cos=tan?

Reply 9

bob9001

Ahhhh yes! This is what I was doing but was confused about the 2 equations I got!

You can't add/subtract them can you?
Can you divide so sin/cos=tan?

why cant you add them or subtract ..
You can

T_1sin30+T_2sin30=4410=>T_1+T_2=8820

T_2\sqrt{3}-T_1\sqrt{3}=450

divide the second equation by

\sqrt{3}

and you get

T_2-T_1=\frac{450}{\sqrt{3}}

Reply 10

OP

rbnphlp

why cant you add them or subtract ..
You can

T_1sin30+T_2sin30=4410=>T_1+T_2=8820

T_2\sqrt{3}-T_1\sqrt{3}=450

divide the second equation by

\sqrt{3}

and you can solve..

Cool thanks :smile:

Reply 11

bob9001

Cool thanks :smile:

no problem :smile:

Reply 12

steve2005

17

bob9001

Nope sorry

I cancelled a two incorrectly.

So now I think/hope the answers are 4280N and 4540N

Reply 13

OP