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Sledge on a slop problem -

A ramp that is 3.25m long leads up to a platform which is 1.25m high. A cubic packing

case of side length 1m that weighs 50kg stands at the top of the ramp. It is held in position

by a rope held parallel to the ramp.

(a) If the coefficient of static friction is 0.35, what is the tension in the rope?

I am trying to understand the solution to this problem, but I don't understand the part where values of

$\displaystyle sin \theta = \frac{5}{13} $

$\displaystyle cos \theta = \frac{12}{13} $

how were these values obtained?

Re: Sledge on a slop problem -

Quote:

Originally Posted by

**Tweety** A ramp that is 3.25m long leads up to a platform which is 1.25m high. A cubic packing

case of side length 1m that weighs 50kg stands at the top of the ramp. It is held in position

by a rope held parallel to the ramp.

(a) If the coefficient of static friction is 0.35, what is the tension in the rope?

I am trying to understand the solution to this problem, but I don't understand the part where values of

$\displaystyle sin \theta = \frac{5}{13} $

$\displaystyle cos \theta = \frac{12}{13} $

how were these values obtained?

How is sine obtained in a right triangle? What about cosine?

If that doesn't make sense, draw a right triangle with leg lengths 5 and 12, and answer the following questions:

(a) What is the length of the hypotenuse?

(b) Consider the acute angle adjacent to the 12-length side. What is its sine? (You should not need a calculator for that.)

(c) What is its cosine?

Re: Sledge on a slop problem -

Hello,

thanks for your reply,

I know it was derived from drawing out a right angled triangle, but I still dont understand what numbers to put in?

As far as i can see, in only know the length of one side? v = 1?

where did 5 and 12 come from in the first place?? Thats what i dont get

Re: Sledge on a slop problem -

Quote:

Originally Posted by

**Tweety** A ramp that is 3.25m long leads up to a platform which is 1.25m high. A cubic packing

case of side length 1m that weighs 50kg stands at the top of the ramp. It is held in position

by a rope held parallel to the ramp.

(a) If the coefficient of static friction is 0.35, what is the tension in the rope?

I am trying to understand the solution to this problem, but I don't understand the part where values of

$\displaystyle sin \theta = \frac{5}{13} $

$\displaystyle cos \theta = \frac{12}{13} $

how were these values obtained?

from what I can tell they are wrong.

You're given the opposite side is 1.25, and adjacent side 3.25.

opp/adj = 0.385

a 5/12/13 triangle has opp/adj = 5/12 = 0.417

so this ramp is not 5/12/13.

Re: Sledge on a slop problem -

Quote:

Originally Posted by

**Tweety** Hello,

thanks for your reply,

I know it was derived from drawing out a right angled triangle, but I still dont understand what numbers to put in?

As far as i can see, in only know the length of one side? v = 1?

where did 5 and 12 come from in the first place?? Thats what i dont get

5-12-13 is a ratio. Not absolute measures. So if you know the length of one side, you can use those ratios to find the other two sides.