1.7.1. Energy
A subsection of Physics, 0625, through 1. Motion, forces and energy
Listing 10 of 184 questions
shows an aeroplane of mass 3.4 × 105 kg accelerating uniformly from rest along a runway. After 26 s it reaches a speed of 65 m / s. Calculate the acceleration of the aeroplane, acceleration = the resultant force on the aeroplane. force = Just after taking off, the aeroplane continues to accelerate as it gains height. State two forms of energy that increase during this time. 1. 2. State one form of energy that decreases during this time. State why the total energy of the aeroplane decreases during this time. When the aeroplane reaches its maximum height, it starts to follow a curved path at a constant speed. State the direction of the resultant force on the aeroplane.
0625_w12_qp_33
THEORY
2012
Paper 3, Variant 3
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State the energy changes that take place when a cyclist rides down a hill without pedalling, a cyclist pedals up a hill at a constant speed. A car of mass 940 kg is travelling at 16 m / s. Calculate the kinetic energy of the car. kinetic energy = The car is brought to rest by applying the brakes. The total mass of the brakes is 4.5 kg. The average specific heat capacity of the brake material is 520 J / (kg °C). Calculate the rise in temperature of the brakes. Assume there is no loss of thermal energy from the brakes. rise in temperature =
0625_w13_qp_31
THEORY
2013
Paper 3, Variant 1
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A child’s toy launches a model parachutist of mass 0.40 kg vertically upwards. The model parachutist reaches a maximum height of 8.5 m. Calculate the gravitational potential energy gained by the model parachutist, energy = the minimum possible speed with which the model parachutist was launched. speed = In practice, the launch speed must be greater than the value calculated in . Explain why. As the model parachutist returns to the ground, it loses gravitational potential energy. Explain what happens to this energy as the model parachutist falls through the air at constant speed.
0625_w13_qp_33
THEORY
2013
Paper 3, Variant 3
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A diver climbs some steps on to a fixed platform above the surface of the water in a swimming-pool. He dives into the pool. shows the diver about to enter the water. 8.0 m The mass of the diver is 65 kg. The platform is 8.0 m above the surface of the water. Calculate the increase in the gravitational potential energy of the diver when he climbs up to the platform. increase in gravitational potential energy = the speed with which the diver hits the surface of the water. Ignore any effects of air resistance. speed = In another dive from the same platform, the diver performs a somersault during the descent. He straightens, and again enters the water as shown in . Discuss whether the speed of entry into the water is greater than, less than or equal to the speed calculated in . Ignore any effects of air resistance.
0625_w14_qp_31
THEORY
2014
Paper 3, Variant 1
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shows a farmer driving a tractor that has a diesel engine. State the unit of energy. State the useful energy obtained from the diesel engine as the tractor starts to move. State two other forms of energy output from the diesel engine. and Complete the following sentence by ticking one box. Modern diesel engines waste less energy than older diesel engines. This means modern diesel engines are faster. more efficient. more reliable. The tractor in is a lot heavier than a car. A car sinks into soft ground. The tractor does not sink. Explain why this is.
0625_w15_qp_22
THEORY
2015
Paper 2, Variant 2
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A load is hung from a spring, as shown in . load The load is pulled down a few centimetres and then released. The spring and load oscillate up and down. State the position of the load when the spring has maximum elastic energy, when the load has maximum kinetic energy. The spring oscillates up and down for a short time. State the principle of conservation of energy. Describe the energy changes as the spring and load oscillate and suggest why the load and spring eventually stop moving.
0625_w16_qp_33
THEORY
2016
Paper 3, Variant 3
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State an expression for the kinetic energy of an object of mass m that is moving with a speed v. State and explain whether kinetic energy is a scalar quantity or a vector quantity. shows two fairground “bumper” cars. stationary empty car 50 kg moving car 200 kg springs 2.5 m / s The car with passengers, of total mass 200 kg, is moving in a straight line. It is travelling at 2.5 m / s when it hits a stationary empty car of mass 50 kg. After the collision, the empty car moves forwards in the same direction at a speed of 4.0 m / s. For the car with passengers, determine its momentum when it is travelling at 2.5 m / s, momentum = the speed and direction of its motion immediately after the collision. speed = direction: Fixed to the front and the back of the cars are large springs. When the cars collide the springs compress. The total kinetic energy of the cars after the collision is equal to the total kinetic energy before the collision. Describe the energy transfers that occur as the cars collide and then separate.
0625_w16_qp_42
THEORY
2016
Paper 4, Variant 2
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shows a fairground ride. cabin path of cabin starting position pylon pylon People sit inside a cabin suspended between two pylons. The cabin is lifted to the starting position shown in . State the name of the type of energy gained by the cabin as it rises. The cabin is released and swings down between the two pylons. The path of the cabin is shown on . The cabin has maximum kinetic energy at one point on its path. Draw this point on and label this point X. A force opposes the motion of the cabin as it falls. State the name of this force. After a few swings, a brake system stops the cabin (not shown on the diagram). Use ideas about energy transfer to suggest how the brake system stops the cabin.
0625_w17_qp_32
THEORY
2017
Paper 3, Variant 2
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Questions Discovered
184