Energy stores and transfersIB MYP Sciences: Subtopic test

1. 1
   A child in Nairobi winds up a clockwork toy car, puts it on the floor and lets it go. The toy speeds across the floor, then gradually slows down and stops.

   (a)

   Which energy store of the toy car increases as the child winds up the spring?

   [1 mark]

   • AKinetic
   • BElastic
   • CChemical
   • DGravitational potential

   (b)

   Which statement best describes what happens to the toy's energy when it stops?

   [1 mark]

   • AThe energy is destroyed
   • BThe energy is all stored in the elastic store again
   • CThe energy has been transferred to the thermal store of the surroundings
   • DThe energy stays in the kinetic store of the car

   (c)

   Describe the energy transfers that happen from the moment the spring is released until the car stops.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A hydroelectric power station in Norway has a reservoir high up a mountain. Water runs down large pipes to turbines at the bottom, and the turbines turn a generator that supplies electricity to nearby towns.

   (a)

   In which energy store is the energy of the water in the high reservoir?

   [1 mark]

   • AGravitational potential
   • BKinetic
   • CElastic
   • DMagnetic

   (b)

   By which energy transfer pathway does the energy leave the generator to reach the towns?

   [1 mark]

   • AMechanically
   • BBy heating
   • CBy radiation
   • DElectrically

   (c)

   Describe the energy transfers from the water at the top of the pipes to the electricity leaving the generator.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A class in Melbourne compares three bouncing balls, X, Y and Z. Each ball is dropped from a height of 1.00 m onto the same hard floor and the height it rebounds to is measured. The students predict that a ball that rebounds lower transfers more energy to the surroundings. The mean rebound heights were 0.80 m for ball X, 0.55 m for ball Y and 0.30 m for ball Z.

   (a)

   Identify the independent variable, the dependent variable and one control variable in this investigation.

   [3 marks]

   (b)

   Describe the trend in the results and evaluate the students' prediction, using ideas about energy.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A taxi company in Bangkok is deciding whether to replace its petrol taxis with battery-electric taxis. A petrol engine takes energy from the chemical store of the fuel. An electric motor takes energy from a battery that is charged from the national grid, where about half of the electricity comes from burning natural gas.

   (a)

   Discuss the benefits and drawbacks of replacing the petrol taxis with battery-electric taxis, and decide whether the company should switch.

   [6 marks]

   (b)

   In one second a petrol taxi engine takes in 1500 J of chemical energy and transfers 375 J as useful kinetic energy and 25 J as sound. An electric motor takes in 1500 J and transfers 1275 J as useful kinetic energy. Using these figures, explain how Sankey diagrams for the two taxis would differ and show that energy is conserved in each.

   [6 marks]

   Total for question 4: 12 marks

End of questions