Kinetic energy = ½ x M x VSquared
Where M = mass of object in kilograms
V= speed of object (ms)
The units used would be kg ms-1 ms-1 or kgms2s-2. This unit is the equivalent of one N
The total amount of mechanical energy is the sum of the potential and kinetic energy.
Energy and work mean the same thing in scientific terms and are interchangeable as concepts, energy being the capacity or ability of a system to do work.
Work = force x distance moved (by the system acted upon by the force) in the direction of force. The rate at which this displacement happens is power. Power can be calculated using the following equation;
P = W/T Where P = power W = Work and T = time. The standard unit for power is the watt (W). This is equivalent to a joule per second. Horsepower is sometimes used as the unit of power when describing machines such as a car. One horsepower is equivalent to approximately 750watts. Humans are machines and could have a power rating, some people are more powerful than others. That is they can do more work in the same amount of time or the same amount of work in less time.
The expression for power is work divided by time. Since the expression for work is force multiplied by displacement, the expression for power can be re-written as force multiplied by displacement all divided by time. Yet displacement divided by time is velocity and so the expression for power can be re-written again differently as force multiplied by velocity.
P = W/T = F x D/T = F x V
Where P = Power
W = Work
T = Time
F = Force
D = Displacement
V = Velocity
This new expression shows that a powerful machine needs a high force and velocity. This means the stronger and faster you are the more powerful you can be.
TASK 1 PART 2
I want to calculate the amount of power used if I run up 10 stairs at a height of 1.65 metres. To do this I need my weight in kg which is 41.2kg I also need the time taken. I was timed running up these stairs and it took 2.5 seconds.
How much power did I use?
(41.2 x 1.65) / 2.5 = 27.192 Watts
I also want to look at the other peoples results so that I can analyse them.
Emma = (50.8 x 1.65) / 2.5 = 33.528 Watts
Adam = (63 x 1.65) / 2.2 = 47.25 Watts
Luke = (74.9 x 1.65) / 2.4 = 61.792 Watts
Elliot = (53.9 x 1.65) / 2.2 = 40.425
Luke used the most power because he is heaviest out of all the subjects and wasn’t particularly fast. This also says he is not very strong. I produced the least power because my body mass is the lowest. Power is important particularly in athletic events such as throwing jumping and sprinting, because these events require explosive movement. From my results I am able to calculate the horsepower produced by myself and the other subjects.
Calculating my Basal Metabolic Rate (BMR)
This is the minimal calorific intake required to sustain life in a resting individual. This is the amount of energy our bodies would require if we slept all day. To work out my BMR I am going to use the following calculation:
65 + (9.6 x weight in Kg) + (1.8 x height in cm) – (4.7 x age in years)=
My BMR is 701.5 calories
This is just one method for calculating my BMR, I choose it because it takes into consideration height, weight and age but it doesn’t consider the amount of physical activity. In a way this makes the calculation not as accurate as is could be. Although there are simpler methods of calculating BMR without using height weight and age which are even less accurate again.
The Role of ATP
When we exercise, where does all the energy that our body uses come from? All Energy comes from adenosine triphosphate ATP. ATP is a complex chemical compound which is formed with the chemical energy we get from food. It is stored in all cells but particularly muscle cells so that it is near by for muscle contraction. When a muscle begins to contract energy is released by the break down of ATP, it is broken down into energy, phosphate and adenosine diphosphate. Our muscle stores enough ATP for two seconds of maximal contraction. However as an athlete we need energy for much longer duration than this, marathon runners for instance are continually using muscle contraction to run for up to six hours. What our body has to do is make more (re-synthesise) ATP.
Our bodies can re-synthesise ATP in two ways;
Adenosine diphosphate can be joined with creatine phosphate (CP), this is a high energy substance stored in the muscles. When they are joined they form ATP. This is the first way the body re-sythesises ATP. This process does not require oxygen so it is said to be anaerobic. However this way of re-synthesising ATP is not that useful to a marathon runner because the supply of CP in the muscles is low, it’s lasts less than ten seconds of maximal activity. On the other hand this type of energy production is useful to an athlete who does events of high intensity effort but, only for a short period of time like long jumpers and 100m sprinters.
The second way our body re-synthesises ATP is by using certain fuel reserves held in the body, proteins, fats and carbohydrates. This can be done with oxygen (aerobically) or without oxygen (anaerobically). In longer duration activities different types of energy supplies would be needed. Carbohydrate is the main supplier of energy during physical activity. It is stored in the muscles and liver as glycogen, it is carried via the bloodstream as glucose. Carbohydrate can be used to create ATP aerobically or anaerobically. The breakdown of glycogen (carbohydrate) to create ATP without oxygen is called anaerobic glycolysis. This process doesn’t produce large amounts ATP. It also creates a waste product of lactic acid, this is what makes our muscles ache as we carry on exercising. A good example of when this system is used is the 400m sprint, 60-90 seconds in the build up of lactic acid inhibits muscle contraction. This is type of production of ATP is for high intensity activities over only a couple of minutes.
If oxygen is present in large quantities, glycogen can be broken down to form ATP without the by-product of lactic acid. This however is complex and time consuming so if the energy is needed quickly and there is not enough oxygen to utilize this system the energy is produced anaerobically. When oxygen is present and ATP is produced there is a by-product but not of lactic acid, of carbon dioxide however this is can be carried away by the blood stream and breathed out. This system can continue until the supply of glycogen or glucose falls short. This is normally for more than an hour (healthy person, good diet, non-smoker, etc).
Fat is another fuel that can be used to aerobically to produce ATP. It is stored as intra-muscular triglyceride inside the muscle, or as adipose tissue which is fat under the skin. It is broken down into fatty acids; these acids then undergo beta oxidation. This is what creates ATP. This is another complex chemical reaction that is also time consuming. An average human stores enough fat for several days of continuous moderate intensity exercise.
Protein is can also be used to re-synthesise ATP for energy in the body. Proteins are store as amino acids. Our vital organs are made up of protein as are our muscles, these we need for our body to function correctly. It process itself is again aerobic, under normal conditions proteins would only supply around 10% of the bodies energy. In cases of starvation this can increase dramatically having a bad effect on the body. Long duration activities rely on aerobic energy sources such as cycling, running, swimming and walking.
So the body has three systems for producing energy (ATP) for exercise. ATP/PC system which is also called the phosphogen system. Anaerobic glycolysis also known as the lactic acid system, and also the aerobic energy systems. Although these are all constantly working once one is completed depleted another is called upon to be the main supplier.
Some sports require a mixture of aerobic and anaerobic energy production, good examples of these are rugby and hockey games where the pace of a player in constantly changing. Anaerobic ATP production allows explosive actions, whilst the aerobic system provides the majority of ATP during phases of recovery and low intensity work. Training can be done that stresses the energy systems relevant the athletes sport, this makes physiological adaptations happen which improves performance.
The table below shows amount of aerobic or anaerobic energy production in certain sports.
Conclusion
Humans need energy to live move and exercise, our body has its own stores of energy which don’t last very long but then the body has its own way of re-making energy, either aerobically or anaerobically to allow exercise to continue.
Bibliography
BTEC ND Sport and Exercise Science textbook by Jennifer Stafford Brown, Simon Rea and John Chance