1.7.1. Energy
A subsection of Physics, 5054, through 1. Motion, forces and energy
Listing 10 of 76 questions
shows the horizontal forces as a cyclist travels forwards. air resistance driving force The cyclist produces the driving force that acts on the back wheel. In this question, you may ignore any frictional force acting on the front wheel. The bicycle accelerates until a constant speed is reached. Describe how the size of the air resistance changes during this time. Compare the sizes of the two horizontal forces when the bicycle is accelerating. The total mass of the bicycle and the cyclist is 75 kg. At one instant, the speed of the bicycle is 4.0 m / s, the driving force is 30 N and the air resistance is 20 N. Calculate the total kinetic energy of the bicycle and the cyclist, the acceleration of the bicycle and the cyclist. As the bicycle moves, energy is transmitted from the pedals to the back wheel. shows what happens to the energy input to the pedals. 400 J of energy input to pedals energy supplied to back wheel 20 J of energy lost As energy is transmitted to the back wheel, some is lost. Explain how this happens. Calculate the efficiency of the bicycle in transmitting energy from the pedals to the back wheel. Some bicycles are made from low density materials. Explain why this is an advantage.
5054_s09_qp_2
THEORY
2009
Paper 2, Variant 0
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illustrates the journey of a cyclist from point A to point B. Points A and B are at the same height. A B The cyclist starts from rest at A and pedals up and over a hill. Near the bottom of the hill, she starts to brake and comes to rest at B. Describe the energy changes that take place as she pedals up the hill at constant speed. Explain how the law of conservation of energy applies to the complete journey from A to B. At one point in the journey, the gravitational potential energy of the cyclist has increased by 5400 J. The mass of the cyclist is 60 kg. The gravitational field strength is 10 N / kg. Calculate the height above A of the cyclist at this point. height above A =
5054_s11_qp_22
THEORY
2011
Paper 2, Variant 2
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shows a windsurfer, sail and board. sail windsurfer board The total mass of the windsurfer, sail and board is 90 kg. They travel at a constant speed of 5.0 m / s. Calculate the total kinetic energy of the windsurfer, sail and board. kinetic energy = The wind exerts a forward force on the sail. Explain, in terms of the forces acting, why the board travels at a constant speed. The wind does work on the sail. Explain, in terms of the conservation of energy, why the total kinetic energy does not increase.
5054_s12_qp_21
THEORY
2012
Paper 2, Variant 1
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In an experiment, a student takes measurements and determines the extension of a spring for different loads. The apparatus is shown in . load spring scale The table in shows the results. load / N 1.0 2.0 3.0 4.0 5.0 length of spring / mm extension / mm Only some of the extensions are shown in the table. Complete the table to show all of the extensions. Calculate the load that produces an extension of 49 mm. load = The student pulls a load downwards from position A to position B and holds it fixed at position B, as shown in . A B The load is stationary at A and at B. The load has no kinetic energy at either point. Place ticks (✓) in the boxes to show how the value of each of the forms of energy compares at A and B. equal at A and B larger at A larger at B energy stored in spring gravitational potential energy of load Work is done by the student to pull the load down. The law of conservation of energy states that energy cannot be created and cannot be destroyed. Explain how this principle applies in this case.
5054_s18_qp_22
THEORY
2018
Paper 2, Variant 2
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Questions Discovered
76