Topics are introduced in terms of their relevance to life in the 21st century. The CD-ROM offers a full range of supporting activities for independent learning, with exemplar examination questions and worked answers with commentary.
The Cambridge International AS and A Level Physics Workbook with CD-ROM supports students to hone the essential skills of handling data, evaluating information and problem solving through a varied selection of relevant and engaging exercises and exam-style questions. Student-focused scaffolding is provided at relevant points and gradually reduced as the Workbook progresses, to promote confident, independent learning.
Answers to all exercises and exam-style questions are provided on the CD-ROM for students to use to monitor their own understanding and track their progress through the course. Skip to content. Toggle navigation. The see-saw is in equilibrium. Determine the force X. For Worked example 4. Use the X pivot 10 N principle of moments to determine the muscular force F provided by the biceps, given the following data: Figure 4.
Step 1 There is a lot of information in this question. The biceps provide a force of N — a force large enough to lit apples! The bar itself is supported with its centre of gravity at the pivot. The sideways. However, the wheel is not in equilibrium. Calculate the driving pair of forces will cause it to rotate. A couple has a turning efect, but does not cause an object to accelerate. To form a couple, the two forces must be: Figure 4. Pure turning efect When we calculate the moment of a single force, the result depends on the point or pivot about which the moment acts.
We can calculate the torque of the couple in Figure object accelerate unless there is another force to balance 4. A couple, however, is a pair of equal and opposite of the wheel: forces, so it will not make the object accelerate. Their resultant can be that is in equilibrium, the sum of the clockwise determined using trigonometry or by scale drawing. Components at right angles to one anticlockwise moments about that same point.
E another can be treated independently of one another. The engine of the ship does not produce any force.
The tension in each cable between A and B and the ship is N. Why should these two components be equal in magnitude? This should be a triangle of forces.
Calculate the magnitude of the force F. It is pivoted a distance of 0. Calculate the force P that is needed at the far end of the bar in order to maintain equilibrium.
The car travels at a constant velocity towards the right Figure 4. Determine the value of the horizontal component of SA the force of the road on the wheel. The centre of gravity of the flagpole is at T a distance of 1. Use your equation to find the tension T in the cable. Two forces, each of magnitude 30 N, are applied normal to the rod at each end so as to produce a turning efect on the rod.
A rope is attached to the edge of the disc to prevent rotation. Calculate: i the torque of the couple produced by the 30 N forces [1] ii the tension T in the rope. SA The strings and the ring all lie on a smooth horizontal surface and are at rest.
The tension in string A is 8. Calculate the tension in strings B and C. The picture is in equilibrium. Label each force clearly with its name and show the direction of each force with an arrow. Calculate: SA i the vertical component of the tension in the cord [1] ii the weight of the picture. Today, many other countries are undergoing the process of industrialisation Figure 5.
Industrialisation began as engineers developed new machines which were capable of doing the work of hundreds of cratsmen and labourers. At first, they made use of the traditional techniques of water power and wind power.
Water E stored behind a dam was used to turn a wheel, which turned many machines. By developing new mechanisms, the designers tried to extract as much Figure 5. If they were less as possible of the energy stored in the water. Steam eficient, their thrust might only be suficient to lit the empty engines were developed, initially for pumping water aircrat, and the passengers would have to be let behind. Steam engines use a fuel such as coal; PL there is much more energy stored in 1 kg of coal than in 1 kg of water held behind a dam.
Steam engines soon not obvious at first that heat, light, electrical energy powered the looms of the textile mills, and the British and so on could all be thought of as being, in some industry came to dominate world trade in textiles. In fact, steam engines Nowadays, most factories and mills rely on had been in use for years before it was realised electrical power, generated by burning coal or gas at that their energy came from the heat supplied to them a power station.
The fuel is burnt to release its store from their fuel. High-pressure steam is generated, and this The earliest steam engines had very low eficiencies 70 turns a turbine which turns a generator. This improvement in energy eficiency has led to At the same time, scientists were working out the basic the design of modern engines such as the jet engines ideas of energy transfer and energy transformations.
We know that the weights have gained change. The gravitational work on the weights even potential energy of the though you may find it tiring weights increases. The gravitational potential energy of the weights is not changing.
Table 5. Your muscles get tired because they are constantly relaxing and contracting, and this uses energy, but none of the energy is being transferred to the weights. Calculating work done Because doing work deines what we mean by energy, we start this chapter by considering how to calculate work done.
A force transfers energy from you to the car. But how much work do you do? Figure 5. So So, the bigger the force, and the further it moves, the work and energy are two closely linked concepts. In physics, we oten use an everyday word but with a special meaning.
Work is an example of this. If you hold a heavy weight above your head where s is the distance moved in the direction of the force. F F c The tension in a string pulls on a stone when E you whirl it around in a circle at a steady speed. Calculate the work done against the force of Energy transferred gravity. PL Doing work is a way of transferring energy. For both 3 A stone of weight 10 N falls from the top of a m energy and work the correct SI unit is the joule J.
Both unit of work or energy the joule are related. To transferred, it follows that a joule is also the amount of determine the work done by the force, it is simplest to energy transferred when a force of 1 newton moves a determine the component of F in the direction of s. What is the a slope. What is the work done by the height and at a constant speed. The work done by the force of gravity?
F Figure 5. Calculate the work N done if the box moves 5. This is the horizontal component of the force: 5. If a gas expands, the walls are pushed outwards — the gas 4 The crane shown in Figure 5.
In a steam engine, to the top of the building from A to B. Distances expanding steam pushes a piston to turn the engine, and are as shown on the diagram.
Calculate how much work is done by the crane. A 30 m Figure 5. The dotted line shows of cross-sectional area A. If 74 we know the force F exerted by the gas on the piston, we 5 Figure 5. Calculate the work done by each force if the box moves 0. Notice that we are assuming that the pressure p does not 6 When you blow up a balloon, the expanding change as the gas expands.
How much expanding against the pressure of the atmosphere, which work is done against the atmosphere in blowing changes only very slowly. You are providing energy an upward force to overcome the downward force of he change in the gravitational potential energy g. We so the force is doing work. You lose energy, and the object gains energy. Worked example 2 shows how to calculate a change in gravitational potential energy — or g.
It should be clear where this equation comes from. You much work he does. By how much does the g. Step 1 As shown in Figure 5. An equal, move upwards at a steady speed. Note that h stands for the vertical height through which the object moves.
Satellites orbit at a height of at least M 1. SA Hint: It helps to draw a diagram of the situation. We can identify other forms of potential energy. An electrically charged object has electric potential energy Step 2 Now we can calculate the work done by the force F: when it is placed in an electric ield see Chapter 8.
Note that the distance moved is in the same direction as the force. So the work done on the weights is about J. This is also the value of the increase in their g. Step 1 Calculate the initial k. Step 2 Calculate the final k. A PL student pulls them apart. Why do we say that Hint: Take care! In this example, the Where has this energy come from? Kinetic energy As well as liting an object, a force can make it accelerate.
M kinetic energy k. Assume that it hits For an object of mass m travelling at a speed v, we have: the ground with a speed of We imagine a car being accelerated as it goes see Figure 5. To give it acceleration a, it to reach the top of the second hill, slightly lower than the is pushed by a force F for a distance s.
It accelerates downhill again. Everybody screams! It transfers energy to the car. Its g. Energy is being transformed from gravitational potential energy to kinetic energy. Some energy is likely to be lost, usually as heat because of air resistance. However, if no energy is lost in the process, we have: E decrease in g.
We can use this idea to solve a variety of problems, as illustrated by Worked example 4. The sphere is pulled to the side so that it is 0.
It is then released. How fast will it 2 As it runs downhill, its g. Inevitably, some energy is lost by the car. So the car cannot return M to its original height.
It is fun if the car runs through a trough of water, but that takes even more energy, and the car cannot rise so high. For example: Figure 5. First at the base. A good supply of energy would be some bars of calculate v 2, then v: chocolate. Each bar supplies kJ. Suppose your weight E 1 2 is N and you climb a m high mountain. Of course, in 5.
Your body is ineicient. A lot of energy is wasted as your muscles example 4 no matter what the mass of the sphere. If we write: eicient as far as climbing is concerned, and you will change in g. And you will need to eat more to get you back 2 down again. Hence: Many energy transfers are ineicient. This is not surprising; we could use the same equation to calculate the speed A car engine is more eicient than a human body, but not of an object falling from height h.
An object of small much more. Repeat with any other value of mass. What happens to this energy if the pilot Figure 5.
Assuming that all transforming her gravitational potential energy becomes kinetic energy during gravitational the dive, calculate her speed just before she enters the water. None of it disappears. We could not have an Figure 5. We are assuming that energy is conserved. It can only be heat escapes into the surroundings. So the car engine is converted from one form to another.
We have previously considered situations where an object is falling, and all of its gravitational potential energy We should always be able to add up the total amount of changes to kinetic energy. In Worked example 5, we will energy at the beginning, and be able to account for it all at look at a similar situation, but in this case the energy the end. We have to think about energy changes within a closed Conservation of energy system; that is, we have to draw an imaginary boundary Where does the lost energy from the water in the reservoir around all of the interacting objects which are involved in go?
Most of it ends up warming the water, or warming the an energy transfer. The outlet Step 1 We will picture 1 kg of water, starting at the of the dam is 20 m below the surface of the water in the surface of the lake where it has g. Then: SA energy that is lost when converted into kinetic energy. When physicists were investigating radioactive decay involving beta particles, they found that the particles ater the decay had less energy in total than the particles before.
Although we cannot prove that energy is always conserved, this example shows that the principle of conservation of energy can be a powerful tool in helping us to understand what is going on in nature, and that it can help us to make fruitful predictions about future experiments. The motor does many thousands of joules of work each second. You are probably familiar with the labels on light bulbs SA he lit shown in Figure 5.
Power is deined as the rate of work done. As a word equation, power is given by: 16 Calculate how much work is done by a 50 kW car work done engine in a time of 1. Power is measured in watts, named ater James Watt, the b State the output power of the engine. If you look back to Question 18 above, you will 18 m in 10 s. Calculate the output power of the motor. A typical diet power: supplies — kcal kilocalories per day.
The motor cannot So we dissipate energy at the rate of about W. Twenty people will keep a room as warm as a 2 kW electric heater.
Note that this is our average power. If you are doing some demanding physical task, your power will be greater. M Moving power Note also that the human body is not a perfectly An aircrat is kept moving forwards by the force of its eicient system; a lot of energy is wasted when, for engines pushing air backwards. We might increase an the faster the aircrat is moving, the greater the power object's g.
Its expended by our bodies. Their gain in height is 3. And, N since our muscles are not very eficient, they need to be supplied with energy even faster, perhaps at a rate of 1 kW. This is why we cannot run up stairs all day long without greatly increasing the amount we eat.
The ineficiency of our muscles also explains why we get hot PL when we exert ourselves. You may have investigated your own power in this way. The crate moves along the surface with a constant velocity of 0.
The N force is applied for a time of 16 s. M a Calculate the work done on the crate by: i the N force [3] ii the weight of the crate [2] iii the normal contact force N. Calculate how long it took to raise the sack to the top of the building. In raising the sack to the top of the building, how much energy is wasted in the motor as heat? Calculate the average power developed by the engine of the car.
The total mass of the cyclist and bicycle is 90 kg. His M potential energy at the top of the pole is J. Sketch a graph to show how his gravitational potential energy Ep varies with h. Add to your graph a line to show the variation of his kinetic energy Ek with h. Explain why the acceleration of the car decreases as the car accelerates.
The level of the water trapped by the dam falls In this way safer cars have been developed and many lives have been saved. This also brought consequences such as the phenomenon of encyclopedism, with the division of knowledge that prevails until today. Physics studies the phenomena of the universe and the laws that govern it. In fact, it explains everything that surrounds us, from the smallest to the most immense; from the indivisible particles to the planets.
The way to materialize the findings occurs through systematic study, using the scientific method for hypothesis testing. Throughout history, physics has explained phenomena such as time, space, matter, energy, movement, light and sound. Similarly, it studies the interaction between these elements, resulting in turn in other phenomena such as gravity, electromagnetism and nuclear forces. Physics is divided into several branches, among which are: acoustics, electromagnetism, mechanics, fluid mechanics, optics, thermodynamics, cosmology, quantum, among others.
As you see, it is a science that encompasses many specialties. Acoustics : Study the nature of sound, where it comes from, how it spreads, etc. Thermodynamics : Studies energy and heat, as well as the systems through which they are preserved and transmitted.
Electromagnetism : Studies energy in matter and space. Fluid Mechanics : Studies the functioning or dynamics of liquid fluids and gases. It also contains a wealth of exam-style questions to test your knowledge and skills to help you fully prepare for the exams.
Fully revised and updated for the new linear qualification, written and checked by curriculum and specification experts, this Student Book supports and extends students through the new course while delivering the breadth, depth, and skills needed to succeed in the new A Levels and beyond. Aqa Physics.
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