# Decelerating a Body at 0.8g

1. Feb 22, 2015

### Lint

I am a truck driver, the law requires me to restrain my load of 100kg, to resist a forward braking force (deceleration) of 0.8g.

If, I took the 100kg load and tilted it (inclined plane), what angle of tilt, would be required to represent a force of 0.8g ?

How does one calculate the angle required to equate to a force of 0.8g, I happen to know the answer is 53 degrees, but, I need to know how this is calculated.

I am a real truck driver with a real problem and look forward to your solution.

2. Feb 22, 2015

### phinds

Do you know any trigonometry ?

3. Feb 22, 2015

Units are important here. After looking at the values on the diagram, I would say that if you want to work with SI units, then the force is really $80g$ Newtons, not $0.8g$ Newtons.
Now that everything is in SI units:
If you're on an inclined plane, your weight could be split into two components (using trigonometry): one parallel to the plane and the other perpendicular to the plane. We only care about whatever happens parallel to the plane for now. Given this information, do you now understand how the angle is obtained?

Last edited: Feb 22, 2015
4. Feb 22, 2015

### jbriggs444

Quibble: If units are important then the force is not 80g either. The force of a 0.8 g acceleration on a 100 kg box is 80 kilogram-g. But this is trigonometry and what really matters are dimensonless ratios like 0.8. The units all cancel anyway.

5. Feb 22, 2015

### phinds

I take it we have now moved into just spoon-feeding answers instead of helping folks figure out how to get answers for themselves.

6. Feb 22, 2015

7. Feb 22, 2015

### Lint

Yes, I have a little knowledge of trig, I am aware that c^2 = q^2 = b^2 and that Sine Theta = Opposite / Hypotenuse and that Cos Theta = Adjacent / Hypotenuse.

8. Feb 22, 2015

### HallsofIvy

l hope that was a typo and you meant c^2= a^2+ b^2 .

9. Feb 22, 2015

### Lint

Indeed, I did Sir, my thumbs are too big !

10. Feb 22, 2015

### Lint

Yes, this is my working -

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11. Feb 22, 2015

### Lint

This is nothing to do with spoon feeding anything, it's to do with providing the most eloquent answer to a specific question, any help you are able to offer is very much appreciated.

12. Feb 22, 2015

### phinds

You are missing the point of this forum, which is not here for the purpose of "providing the most eloquent answer to a specific question" but rather for the purpose of helping people figure out how to GET answers to their questions. We're not giving away fish, we're teaching people how to fish.

13. Feb 22, 2015

### Lint

You are missing the point of this forum, which is not here for the purpose of "providing the most eloquent answer to a specific question" but rather for the purpose of helping people figure out how to GET answers to their questions. We're not giving away fish, we're teaching people how to fish.

I came to this forum for assistance to solve my problem, my knowledge of maths and trig is limited, as I am sure your knowledge of the trucking industry is limited, but if you were ever to ask me which fuel filter should be used for a Detroit 600 diesel engine, I would quite happily tell you.

If you are able to show me how to solve my problem then, I would very much appreciate your help.

14. Feb 22, 2015

### phinds

If I were looking for an answer about trucking, and I just wanted the answer with not expectation of ever having to solve my problem again, then I'd seek out a forum which exists for the purpose of answering such questions, not one that exists for the purpose giving explanations of how trucks work and how to solve my problem.

As for your particular problem, it looked to me as though you already solved it. Is that not so?

By the way, the "quote" button allow you to show someone's post as a quote so you don't have to cut and paste it, which gets confusing.