ATAR Notes: Forum

VCE Stuff => VCE Science => VCE Mathematics/Science/Technology => VCE Subjects + Help => VCE Physics => Topic started by: IntoTheNewWorld on January 20, 2009, 06:41:34 pm

Title: Forces question
Post by: IntoTheNewWorld on January 20, 2009, 06:41:34 pm

a 4.0 kg magpie flies towards a very tight plastic wire on a clothes line. The wire is perfectly horizontal and is stretched between poles 4.0 m apart. The magpie lands on the centre of the wire, depressing it by a vertical distance of 4.0 cm. What is the magnitude of the tension in the wire?

I'm a bit lost

Title: Re: Forces question
Post by: hard on January 20, 2009, 06:54:18 pm

just use e=mc2

Title: Re: Forces question
Post by: phagist_ on January 20, 2009, 06:56:43 pm

You know the gravity force (m*g) you can use trig to find out the angles the wire makes with the horizontal and hence the tension in the string.

Title: Re: Forces question
Post by: NE2000 on January 23, 2009, 09:31:05 am

Quote from: SmRandmAzn on January 20, 2009, 06:41:34 pm

a 4.0 kg magpie flies towards a very tight plastic wire on a clothes line. The wire is perfectly horizontal and is stretched between poles 4.0 m apart. The magpie lands on the centre of the wire, depressing it by a vertical distance of 4.0 cm. What is the magnitude of the tension in the wire?

I'm a bit lost

W = 40 N

Make a diagram, the magpie in the middle depressing the wire held by poles. You can see the two right-angled triangles. Work out the angle between the horizontal and the depressed wire. You know that the vertical component of tension on either side is 20 N. You use that and the angle and trig to find the hypotenuse or the total tension, that gives you 1000 N as the hypotenuse. I'm not sure whether you are meant to double after that or not.