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# Hard question- Mechanics- ENGAA watch

1. Hi guys im unsure how to start to tackle question 4 part d. I will attach my working for the rest of the question. The correct answer is D.

2. (Original post by Shaanv)
Hi guys im unsure how to start to tackle question 4 part d. I will attach my working for the rest of the question. The correct answer is D.

What's the question?
3. (Original post by RDKGames)
What's the question?
Would help😂

4. Treat the cyclist as a projectile being thrown down a slope at an angle the slope with speed . Then you want to find the point between B and C when the distance between them and the slope is the greatest.
5. (Original post by Shaanv)
Hi guys im unsure how to start to tackle question 4 part d. I will attach my working for the rest of the question. The correct answer is D.

For C) why don't you consider the cyclist accelerating parallel to the slope, if you do you get the answer E which is wrong.
6. (Original post by RDKGames)
Treat the cyclist as a projectile being thrown down a slope at an angle the slope with speed . Then you want to find the point between B and C when the distance between them and the slope is the greatest.
Sorry i an still lost.

Im unsure how to find an expression for the distance of the cyclist above the slope. Having this i could differentiate to find a maximum.

I dont know if this is what im meant to do. Could u give me a further hint
7. (Original post by haarithiop)
For C) why don't you consider the cyclist accelerating parallel to the slope, if you do you get the answer E which is wrong.
The way i did it seemed the easiest, so i went with it cus it doesnt accelerate horizontally.
8. (Original post by Shaanv)
The way i did it seemed the easiest, so i went with it cus it doesnt accelerate horizontally.
Isn't it accelerating parallel to the slope as it has a component of weight parallel to the slope.
9. (Original post by Shaanv)
Sorry i an still lost.

Im unsure how to find an expression for the distance of the cyclist above the slope. Having this i could differentiate to find a maximum.

I dont know if this is what im meant to do. Could u give me a further hint
First of all, you need to work parallel and perpendicular to the slope (atleast this is what I'd find easier). Then write down your SUVAT for parallel and then the perpendicular motion, but before then, keep in mind that affects both parallel and perpendicular motion so you need to resolve the gravitational field force wrt to the slope to get your acceleration parallel and perpendicular to the slope.

Then, you can differentiate your expression for perpendicular displacement and find the TIME when the max point occurs, and sub this time into your expression for the parallel displacement. Form there, you should be good.
10. (Original post by haarithiop)
Isn't it accelerating parallel to the slope as it has a component of weight parallel to the slope.
I will try it this way and let u know what i get
11. (Original post by haarithiop)
For C) why don't you consider the cyclist accelerating parallel to the slope, if you do you get the answer E which is wrong.
I tried it parallel and i almost got E as my answer. However it was subtly different from E, so i use some trig and managed to reduce it to C.

12. (Original post by Shaanv)
I tried it parallel and i almost got E as my answer. However it was subtly different from E, so i use some trig and managed to reduce it to C.

Ah my method was right I just made an algebra mistake when simplifying. I get C now. How did you get the same answer without considering the acceleration parallel to the plane?
13. (Original post by haarithiop)
Ah my method was right I just made an algebra mistake when simplifying. I get C now. How did you get the same answer without considering the acceleration parallel to the plane?
Instead of resolving parallel and perpendicular to the slope, i resolved horizontally and vertically.

As there is no horizontal acceleration the problem is much simpler, but resolving perpendicular and parallel helps in the later parts of the question.

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