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VCE Stuff => VCE Science => VCE Mathematics/Science/Technology => VCE Subjects + Help => VCE Physics => Topic started by: Chavi on May 29, 2010, 07:15:59 pm

Title: Tension
Post by: Chavi on May 29, 2010, 07:15:59 pm: Can I please get some help with the following question?

A car of mass 700kg is towing a trailer of mass 500kg, on an incline of 30 degrees to the horizontal.
Friction on the trailer is 400n, friction on the car is 600n. If the engine provides a driving force of 700n, what is the tension in the towbar?

Thanks in advance,
Title: Re: Tension
Post by: lachymm on May 29, 2010, 11:07:51 pm: This appeared at first to be simple but it is abit out of the ordinary here is my attempt at solving it,
I am assuming that the velocity of the car and trailer isnt constant as forces are unbalanced...(more friction than driving force)
Therefore Force going in uphill direction = 700 N
Force (or friction) going downhill = $400+600+sin(30)*12000$
=7000N
However These are irrelevant as we are interested in the difference of the net forces acting on the trailer and car
Let up hill be negative and downhill be positive
Net force acting on the car is equal to $600+7000*sin(30)-700=3400$
Net force acting on the trailer is equal to $400+5000*sin(30)=2900$
Car has more force than trailer downhill therefore 0 tension in the tow bar as the car and trailer will both be going backwards, i feel as if you are leaving some information out...is the car going downhill or up hill etc...
Title: Re: Tension
Post by: googoo on May 30, 2010, 08:51:27 pm: must be going downhill, T = 275 N.
Title: Re: Tension
Post by: m@tty on May 30, 2010, 09:14:17 pm: Is it even possible to have MORE friction than the force applied?
Title: Re: Tension
Post by: googoo on May 30, 2010, 09:19:52 pm: yes going downhill
Title: Re: Tension
Post by: m@tty on May 30, 2010, 09:22:07 pm: Ah, I see.
Title: Re: Tension
Post by: TyErd on May 30, 2010, 09:25:18 pm: is 275N correct? can someone confirm, im getting an answer of 2735N hmmm.
Title: Re: Tension
Post by: TyErd on June 02, 2010, 09:14:12 pm: can anyone confirm at all?
Title: Re: Tension
Post by: kenhung123 on June 02, 2010, 10:36:10 pm: Can I just ask..is there a formula to find the tension in a string and a circularing object such as one spinning around a pole?
Title: Re: Tension
Post by: m@tty on June 02, 2010, 10:37:36 pm: The tension in a rope spinning something around is the centripetal force.
Title: Re: Tension
Post by: kenhung123 on June 02, 2010, 10:42:42 pm: Oh sorry I mean like umm...when the ball is banked and the centripetal force is like the horizontal force
Title: Re: Tension
Post by: TyErd on June 07, 2010, 08:55:46 am: Quote from: Chavi on May 29, 2010, 07:15:59 pm

A car of mass 700kg is towing a trailer of mass 500kg, on an incline of 30 degrees to the horizontal.
Friction on the trailer is 400n, friction on the car is 600n. If the engine provides a driving force of 700n, what is the tension in the towbar?

Can someone tell me what answer they get for this one?
Title: Re: Tension
Post by: curious111 on June 07, 2010, 07:09:56 pm: Net force acting on system = 700N + 12000sin(30)N - 1000N
= 5700N down slope

Therefore System accelration = 4.75 m/s^2

Isolate the trailer:
It has an acceleration of 4.75 m/s^2, therefore the Net Force acting on the trailer = 4.75 x 500 = 2375

Therefore, Net Force = Tension + Wx component - Friction
2375 = Tension + 5000sin(30) - 400

Tension = 275N

Can anyone confirm this working out is correct?
Title: Re: Tension
Post by: TyErd on June 07, 2010, 08:25:38 pm: Yes thats what I got as well