17772 questions

How do we breathe in?

The scientific term for breathing in is inspiration. The main muscle that helps us to breathe is called the diaphragm; a large, dome shaped muscle that sits below our rib cage. The external intercostal muscles also help us to breathe, though they don't have as much influence as the diaphragm. These muscles are the outer parts of the intercostal muscles, which sit between our ribs. *show diagram positioning diaphragm and intercostal muscles.*Inspiration is a passive process, and is a result of changes in pressure within the thoracic cavity, which is where the lungs sit. There are 2 gas laws that you need to know to understand inspiration. The first is that when the volume of a space increases, the pressure inside decreases. The second is that gas will move from an area of high pressure to low pressure. This is why the mechanism of inspiration works. The diaphragm contracts and flattens out, pushing down the organs below. The external intercostal muscles also contract, and pull the rib cage upwards and outwards. This increases the size of the thoracic cavity, reducing the pressure to below the atmospheric pressure. Air then rushes from high to low pressure, down the trachea and into the lungs. Do you have any questions about that? *ask them to repeat it back to me*.
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Hannah E.

Answered by Hannah, Biology tutor with MyTutor


State an explain the result of an increase in temperature on the following equilibria: N2 (g) + 02 (g) <-> 2 NO (g) (delta H = +180kJmol-1)

An increase temperature favours the endothermic direction of an equilibrium reaction; this is because there is more energy in the surroundings to accommodate for the energy that will be taken into the system during the reaction.
From the positive delta H value we can see that the forward reaction is endothermic. This is because there is an increase in enthalpy, meaning energy is taken in from the surroundings as the reaction progresses.
As a result, the position of equilibrium would move to the right, as the forward reaction is favoured.
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Samuel G.

Answered by Samuel, who has applied to tutor Chemistry with MyTutor


Write me a descriptive piece of writing.

I would then check the students piece of writing, pointing out the need for paragraphs. We could then brainstorm different adjectives they could have used. I would also tell them my trick to describe the 5 senses to create a more rounded piece of descriptive writing.
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Jemima W.

Answered by Jemima, English Literature tutor with MyTutor


Which is heavier, a ton of feathers or a ton of lead?

They're both the same.
The feathers would take up a lot more space though! Feathers have a lower density than lead (i.e. for the same volume, feathers are less heavy). In practice, if you drop a tonne of feathers and a tonne of lead from the same height at the same time (on Earth), the feathers will be pushed around more by air resistance and will take longer to reach the ground. But if you did that experiment somewhere without air resistance (e.g. another planet) you'd see that they would take the same amount of time, because they would have the same weight (and mass).
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Francis N.

Answered by Francis, Physics tutor with MyTutor


How fast would you have to launch a rocket to escape the Earth's gravitational pull?

Newtons law of gravitation tells us that F = G m1m2/ r2 (where G is the universal gravitational constant, m1 the mass of the Earth, m2 the mass of the rocket, and r the distance between the centre of the rocket and the centre of the Earth, so that's a good starting point: in order to escape the earth's gravitational pull, our rocket must be pushed out by a force equal to or greater than that. Can we use this formula directly? Well we actually could in theory, but that gets a bit complicated because as your rocket goes higher, r changes.
So how else can we think about this? Well, conservation of energy tells us that in order to escape the Earth's pull, the kinetic energy of the rocket must be greater than/equal to the gravitational potential energy. The GPE = G m1 m2 / r (derived from the law above, but you don't need to know the derivation, all the info for this is in your formula book), so we say that G m1 m2 /r = 1/2 m2 v2. Rearranging that formula for v, we get v = sqrt(2 G m1/r). And that's your escape velocity!

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Francis N.

Answered by Francis, Physics tutor with MyTutor


Show that the two vectors A= 2i+3j-k and B=3i-j+3k are perpendicular

We know that two vectors are perpendicular when their dot product is equal to 0. As you can see from the SQA Higher Maths formula sheet, the equation for the dot product is; A.B=a1b1+a2b2+a3b3.To answer this question we just substitute in the values of both vectors. Since A = (2,3,-1) we have a1 = 2, a2 = 3 and a3 = -1 (if the student doesn't understand how to convert i,j,k vectors into column or row form I would explain this here) and for B =(3,-1,3) we have b1=3,b2=-1,b3=3. Thus putting this into the equation we get A.B= (2x3)+(3x-1)+(-1x3), by multiplying this out we get A.B= 6 -3 -3 = 0. Thus since A.B=0, the two vectors are perpendicular.
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Samantha C.

Answered by Samantha, who has applied to tutor Maths with MyTutor

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Differentiate xcos(x) with respect to x.

Here we have the product of two functions, and require use of the product rule. This is, for y=f(x)g(x), dy/dx=f'(x)g(x)+f(x)g'(x). This essentially means, take one part and differentiate it and multiply it by the other part, and then add that to the other part which is the same as the first, just with the other part differentiated. In this case we have f(x)=x and g(x)=cos(x). This means that f'(x)=1 and g'(x)=-sin(x). If we now apply this into the formula we get dy/dx=cos(x) - xsin(x).
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Oliver S.

Answered by Oliver, who has applied to tutor Maths with MyTutor

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Describe and evaluate the psychological explanations of obesity

Essay Plan
AO1 - "Describe" - the psychological explanations of Obesity
Point 1:    
Restraint Theory - Herman and Polivy, people attempt to lose weight by limiting the amount they eat which is counterproductive.
Cognitive Control - Restrained eaters set themselves beliefs that categorise foods into good and bad - consciously thinking about their weight and eating.
Paradoxical Outcome - this results in the restrained eater becoming more preoccupied with food rather than less. By placing limits on what and how much they eat, the restrained eater no longer eats when they are hungry and stops when they are satiated
Link: Their eating is no longer under physiological control they actively ignore these indicators of hunger which leads to disinhibition of eating behaviour.
Point 2:     
After a period of restrained eating it is often followed by disinhibition - the individual eats as much as they want, "binge eating"
Restrained eaters are vulnerable to internal and external food related cues such as mood (internal) and smells (external). e.g. individual can eat more to increase their dopamine levels when they are sad.
These cues are disinhibitors and lead to loss of control over restrained eating.
Cognitive Process - All or Nothing thinking, fails one day to keep their restriction are more likely to binge because they see themselves as already having failed
Link: Herman and Polivy describe restrained eaters as being different from the psychological norm of eating behaviour.
Point 3:
Boundary Model - food intake exists on a continuum from hungry to full
Biological process determine how much we eat at each end of the continuum
Energy levels low= aversive state of hunger - motivated to eat
Eating to fullness= aversive state of discomfort - stop eating
Biological indifference - between these two points, biological processes have minimal effects, but cognitive and social factors have their greatest influence.
Restrained eaters - low hunger boundary - less responsive to feelings of hunger BUT have a higher satiety boundary - need more food before full.
Have a wider zone of biological indifference - eating comes under cognitive rather than physiological control making them more vulnerable to effects of disinhibition.
AO3 - "Evaluate"
Supporting Research: Wardle and Beales - 27 Obese women, divided into group of restrained and non-restrained eaters. Restrained eaters consumed the most calories overall, generally ate less throughout 7-week experimental period but experienced occasional "binge"- increase in food consumption past satiety.
Contradictory Evidence: Savage et al. - Longitudinal study into restrained eating, 163 women, measured weight, dietary restraint and disinhibition every 2 years over a 6 year period. found increase in restraint lead to a decrease in weight. - Could be due to social desirability bias in participants.
Evolutionary Approach - During the EEA humans did not have a regular food source, would often have periods of starvation and then binged on food when they had more. Lead to an evolutionary adaptation in humans that when they restrict themselves their evolutionary response is to then eat more food.
Nature vs Nurture
Nurture Argument - Social Learning theory - environmental triggers cause restrained eaters to eat more. Boyce and Kuijer - showed restrained and unrestrained eaters’ images of models in the media before giving them a ten minute taste test where they could eat as much as they wished. Found restrained eaters ate more.
Nature Argument - Evolutionary - increase in consumption after periods of restraint are due to a biological adaptation in human evolution due to changing food availability in the EEA.
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Hannah S.

Answered by Hannah, Psychology tutor with MyTutor


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