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# AS and A Level: Mechanics & Radioactivity

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## Newton's first law

1. 1 The law is: A body at rest will remain at rest or continue to move with constant velocity unless acted on by an unbalanced force.
2. 2 If the forces acting on a body are balanced, the body is in a state of equilibrium. The resultant force is then zero and there is no acceleration.
3. 3 Exam questions expect you to recognise equilibrium even when it is not mentioned. e.g. ‘A cyclist pedals up a slope with a steady speed’ indicates equilibrium because steady speed in a straight line is constant velocity.
4. 4 Steady speed does not always mean constant velocity. A car travelling in a circular path at a steady speed does not have a constant velocity because the direction is changing. So the forces on the car are unbalanced.
5. 5 There are many familiar examples of Newton’s first law: 1) occupants not wearing a seatbelt in a moving car will continue to move forward when the car stops suddenly because there is no force to change their motion. 2) Shake water off an umbrella by opening and then quickly closing. Water droplets carry on moving away when umbrella is suddenly closed.

## Newton's second law

1. 1 The law is: The acceleration of a body is directly proportional to the resultant force acting on it and in the same direction as this force.
2. 2 When the forces on a body are unbalanced, this law allows the acceleration to be calculated using F=ma. Remember that F is the vector sum (resultant) of all forces acting.
3. 3 You may be expected to know the base units of force.
Since F=ma, in units we can write: N = kg ms-2.
4. 4 F=ma can be experimentally verified. 1) Using a trolley of mass m, keep m constant and measure acceleration for increasing force. This shows a is proportional to F. Then, keeping F constant, measure a for increasing values of m. This shows that a is inversely proportional to m. Combining results shows that F is proportional to ma. The Newton is defined as the force that produces an acceleration of 1 ms-2 when acting on a mass of 1kg.
5. 5 Newton’s first law and Newton’s second law predict the same outcome when the resultant force is zero. The acceleration is then zero and the body’s velocity remains constant.

## Newton's third law

1. 1 The law is: If body A acts on body B then body B will act on body A with a force of the same magnitude and opposite direction.
2. 2 Every force is paired with another force. They are referred to as action and reaction forces. We don’t need to consider the paired force if we are only considering forces on one body.
3. 3 If two forces are a Newton’s 3rd law pair, they must obey these 5 criteria: They will have the same magnitude, same line of action and the same nature (type). They must each act on a different body and in opposite directions. If any of these are not true, then the forces are not a Newton’s 3rd law pair.
4. 4 A free body diagram does NOT show Newton’s 3rd law pairs of forces because all of the forces are acting on the same body. Just because two forces balance does not make them a Newton’s 3rd law pair. Newton’s 3rd law pairs can be described in words by including both bodies, the nature of the force, the size and direction. For example, The Moon exerts a gravitational force on the Earth and the Earth exerts an equal and opposite gravitational force on the Moon.
5. 5 Familiar examples. Walking: your shoe push the ground backwards by friction and the ground pushes your shoes forward. Thrust on a rocket: the rocket pushes hot gas particles downwards by normal contact and the same normal contact of the particles pushes the rocket upwards. Weighing scales push up on your feet by normal contact so your feet push against the scales. The scales are measuring the normal contact force not weight!

• Marked by Teachers essays 2
• Peer Reviewed essays 9
1. ## AS OCR B Advancing Physics Coursework - Making Sense of Data

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curved line of best fit to the graph, showing positive correlation between the distance fallen and the velocity of the object as it passed through the light gate. The line is curved until about 0.3 metres but then becomes more linear, which would be expected if acceleration due to gravity is constant - as a straight line shows constant acceleration. The velocity values from smaller distances appear to be anomalous, suggesting some error involved in the experiment. This could be because any errors in height make up a larger proportion of the overall distance the mass had fallen when dropped from lower heights.

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2. ## Torsional Pendulum final experiment

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It will eliminate the human error as the error due human reaction time will no longer apply. There will only be a reading error now, which is far less significant than the experimental error. * I will use a range of lengths from 100-500mm rather than 100-800mm, as when the length becomes very long the bar on the bar on the wire tends to wobble a lot more than when a shorter length is used. Therefore I am hoping this will further reduce the error in the time period.

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3. ## Are mobile phones a health risk?

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Main Points How might Mobile Phones be Hazardous to our Health? After studying numerous publications, I have found that if there are concerns about how mobile phones may pose a risk to the health of their users, they can be divided into two categories: The first is Electromagnetic Radiation from the phone damaging human cells and cause cancers and tumours. The second is that the EM radiation from the handset creates a heating effect. What is EM Radiation? EM radiation is something we are exposed to all the time: TVs, radios, satellite communications, etc all use EM waves to transmit information.

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4. ## The Physics of Windsurfing

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The net force propels the windsurfer, but part of this force is to the side of the sailboard. The dagger board keeps the board from moving sideways. The dagger board extends from the sailboard down into the water. The dagger board not only keeps the board from drifting sideways, but it also a device used to turn the board so that one may steer. You steer by tipping it forward and back. The sailboard doesn't move across the water by simple a force of wind that pushes on the sail.

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5. ## Physics nptes key definitions. Newtons Law And Momentum, Circular Motion And Oscillations, Thermal Physics

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* Newton's Third Law - When body A exerts a force on body B, then body B exerts on body A force that is equal, opposite in direction and of the same type * The Principle Of Conservation Of Momentum - In any direction, in the absence of external forces, the total momentum of a system remains constant * Elastic Collision - No momentum or kinetic energy is lost * Inelastic Collision - Momentum is conserved, but kinetic energy is not Module 2: Circular Motion

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6. ## The acceleration of a ball down various inclines

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The acceleration of the ball is determined by further analysing these results. INTRODUCTION My Semester 2 Science Assessment Task requires me to research and investigate an experiment of my own interests and analyse certain scientific principles concerned with this task. The experiment I conducted tests the change of velocity of a spherical object down a slope, and how that is affected by different inclines. The reason I chose this experiment was because I found motion, and how forces induce it, to be very interesting. Possibly being able to mathematically link different rates of acceleration, and maybe being able to calculate the forces exerted on an object during decline is certainly a very enticing prospect, considering this is more useful than many skills I have acquired in my lifetime.

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7. ## Aim:To find out whether or not the angle of the ramp affects the acceleration of the trolley.

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Every 2 dimensional movement (ignoring the fact the trolley can go side to side) has 2 directions: X and Y. In this experiment Y will be gravity and X will be determined by the angle of the ramp. If the ramp is steeper than the net movement of the trolley will be forwards and downwards; and as the ramp will be steeper this will allow the Y force of gravity to pull the object quicker; as the area of the ramp will be cleared in a quicker time.

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8. ## Catapult Investigation

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back the more potential energy it stores when released more potential energy is changed into kinetic energy and therefore more kinetic energy is used to move the weight. I predict that as the elastic band gains more potential energy (pulled back further) it will fire the weight further (more kinetic energy). If you double the force put on the elastic band and if you double the distance that it is pulled back then the distance that the weight is fired will quadruples."

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9. ## Isaac Newton.

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Upon the death of his stepfather in 1653, Newton lived with his mother, his grandmother, one half-brother, and two half-sisters. Shortly after this time Isaac began attending the Free Grammar School in Grantham. During this time Isaac lodged with the Clark family at Grantham. However he seems to have shown little promise in academic work. An uncle, William Ayscough, decided that Isaac should prepare for entering university and, having persuaded his mother that this was the right thing to do, Isaac was allowed to return to the Free Grammar School in Grantham in 1660 to complete his school education.

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10. ## Sir Isaac Newton.

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There is no doubt that Isaac felt very bitter towards his mother and his stepfather Barnabas Smith. When examining his sins at age nineteen, Isaac listed: - Threatening my father and mother Smith to burn them and the house over them. Upon the death of his stepfather in 1653, Newton lived in an extended family consisting of his mother, his grandmother, one half-brother, and two half-sisters. From shortly after this time Isaac began attending the Free Grammar School in Grantham.

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11. ## Physics in Sports. The law of conservation of energy also plays a major role in sports. In football if you kick a ball you are transferring kinetic energy from your foot to the ball.

If thrown at any other angle than 90� it will have a parabolic path (trajectory). Also air resistance and friction will reduce the rate at which the ball moves. The law of conservation of energy also plays a major role in sports. In football if you kick a ball you are transferring kinetic energy from your foot to the ball. From the pendulum balls by the side you can see how energy transfer works. If you lift the ball at left then energy will be passed on to the neighbouring ball and as a result the ball at the end will move the same distance from which it was released on the other side.

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13. ## Gravitation - Kepler and Newton revision notes and calculations.

This is due to the fact that we are nearer the earth centre than the moon (about 1:60) Newton wanted to find out a relation between the distance and the gravitational force (of acceleration due to gravity g) First trial: Second trial: He found that: Newton's Law of universal gravitation Every particle of matter in the universe attract every other particle with a force which is directly proportional to the product of this masses and inversely proportional to the square of their distance apart And ==> G is defined as the gravitational constant = 6.7 Relation between Newton's Law of gravitation and Kepler's Law & ==> =Constant E.g.

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14. ## CIRCULAR MOTION - revision notes and calculations

(if ?? is very small) Therefore, a = change of velocity/time taken = ?V/?t = V??/?t = V? i.e. a = V? = V2/r = r?2 (in magnitude) Note: (I) For direction, if ?t is made so small that A and B almost coincide, then, the vector ?V is perpendicular to VA (or VB) i.e. the direction is pointing to the centre O. (II) The acceleration is pointing to the centre, which is therefore known as centripetal acceleration. (III) According to Newton's 2nd law, acceleration is due to force, namely the resultant force Therefore, F = ma = mV2/r = mr?2 This is known as the centripetal force (IV)

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15. ## Radiotherapy is the use of high energy x-rays and similar rays such as electrons to treat diseases.

Radiotherapy works by destroying the cancer cells in the treated area. Also normal cells can also be damaged during the treatment but they can usually repair themselves. It can cure some cancer; it also can be used to diminish cancer symptoms. Radiotherapy treatment can also lessen the possibility of cancer coming back subsequent to surgery Radiation therapy kills cancer cells by damaging or destroying their DNA. It also could affect your regular cells in your body. Also, radiation therapy may not destroy or damage a cancer cell right away.

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16. ## Objective To measure the centripetal force for whirling a mass round a horizontal circle and compare the result with the theoretical value given by F= mw2r .

The formula can also be expressed in the terms of the velocity v of the mass, where ?=v/r . Substituting ?=v/r into the formula for F , F = mv2/r The string may not be horizontal as the rubber bung moves around. In fact, the bung moves in a circle of radius r = L sin?. The tension T thus provides both the centripetal force and a force to support the weight of the bung. By resolving T into its horizontal and the vertical components, it is easy to show that T = m?2L regardless of the angle ?.

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17. ## Centripetal motion. The objective of this experiment is to verify whether the tension in a centripetal force apparatus is equal to the weight of the mass.

= mr?2 T sin? = m(l sin?)?2 T = ml?2 Apparatus: Rubber bung x 1 Glass tube (15cm long) x 1 Nylon thread (1.5m) x 1 Slotted mass (50g) x 4 Hanger (150g) x 1 Paper clip x 1 Meter rule x 1 Stop watch x 1 Adhesive tape x 1 Balance x 1 Procedures: 1. The mass of the rubber bung (m) was weighed and recorded. 2. The centripetal force apparatus was constructed following the sequence from A to E as shown in Fig.1. A small rubber bung was attached to the upper end of a nylon thread passing through a thin glass tube.

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18. ## Physic lab report - study the simple harmonic motion (SHM) of a simple pendulum and to investigate the phase relationship between the displacement, velocity and acceleration, and to investigate how acceleration is related to displacement in a simple harmo

Points P and R are points where the maximum displacement (amplitude A) can be obtained. Theoretically, the following equations are true for S.H.M.: When the motion starts at the equilibrium position (point Q) x = A sin ?t where ? is angular velocity v = ? A cos ?t a = - ?2A sin ?t Period T = 2 ? / ? Fig. 1 When the motion starts at the position where the amplitude is obtained (point P or R) x = A cos ?t where ? is angular velocity v = ?

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19. ## Use of technology in a hospital radiology department. The department of imaging is one of the best equipped in the UK and provides a very full range of diagnostic and interventional services which include: X ray, Computer Tomography(CT), Magnetic Resonanc

Together these cross section give a very accurate picture of where the infected part of the body and how big it is. PET scan, this is different from CT scan developed in the 1970s. It can show how the body tissues are working, as well as what they look like, PET scanner are very expensive and only a few hospital in the UK have one. A PET scan can help to show up cancer, stage a cancer and decide the best treatment for your cancer The radiology department, also known as the x-ray or imaging department, which carries out the

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20. ## How successful was the management of the Chernobyl Incident?

Yet, this was merely not really effective as sped the breakup of Soviet Union. In my opinion, I think the government overspent and should have used short but effective tactics In helping in the era of thyroid cancer. For example, maybe they should have compensated less and spent more money on health and cleanup. Still, today, radioactivity threatens to collapse the Sarcophagus, a concrete built after the incident used as a 'shelter'. The government are getting a replacement; an arched structure will be used to slide over the sarcophagus.

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21. ## Force of Friction experiment

Kinetic friction Generally, the friction acting on a resting block is less than until the block starts to move. Once the body starts to move over the rough surface, the friction would decrease slightly to a value known as kinetic friction . So is slightly less than but it is still approximately proportional to R. where is the coefficient of kinetic friction at the contact surface. remains constant even the applied force is increased further. is slightly less than . 3. Procedure A. Effect of applied force on friction 1. The set up is connected as shown below. 2.

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22. ## The target of my coursework is to find the amount of g acting on a trolley by comparing the angle of the slope, the distance of the slope and the speed it was travelling as it passes through a light gate

I predict there should also be a slight increase in the trolleys final velocity Planning Equipment needed * I shall need a ramp which is around 1 meter in length, of which will be able to keep the trolley travelling with the lowest amount of friction possible, to ensure the test as fair and accurate as possible * A light gate (to measure the final velocity of the trolley), must be able to be held above the ramp * A trolley to push down the ramp, of which will also need to give as little friction as possible * Card

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23. ## Multi-bladed Pumps. Does the number of propellor blades affect the efficiency of a water pump?

I couldn't rely on distorting my results to fit a simple law, so my experimentation had to be rigorous. Limitations It was important to find a subject that was practical to investigate at school. While I was watching water swirl down the drain as I filled the kettle at home, I wondered how widely-used machines like ship's propellers cope with the unpredictable world of chaos. Propellers have an unusual and distinctive shape designed to reduce turbulence. I wanted to investigate why this particular shape works so well - and if it can tell us anything about turbulent flow. Conveniently, water and propellers are easy-to-use in school labs (or so I thought!).

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24. ## Calculating the Young Modulus of Constanton

It can also be calculated by working out the gradient on the stress-strain graph. When a wire obeys Hooke's Law it deforms elastically. This means that when the load is removed, the wire returns back to its initial length. The atoms in the wire move small distances from their equilibrium positions but then return. After the elastic limit the wire starts to deform plastically. The atoms move within the structure so they cannot return when the load is removed. Measurements Throughout the experiment these measurements will need to be taken and observed: * Stress - Force and surface area * Strain - Initial length and the extension * Young's modulus * Percentage error - error of each piece of equipment * Hooke's law (F=ke)

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25. ## Examining the Behaviour of Mass oscillating on a Spring

Calculate the square of the period T� and draw a graph to check that it is proportional to m 6. Calculate the gradient of the graph, hence calculating the constant k 7. Do the Hooke's law experiment to check whether you are right.

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