Kinetic and gravitational potential energyIB MYP Sciences: Subtopic test

1. 1
   A roller coaster car at a theme park in Orlando is pulled slowly to the top of the first hill by a chain. It is then released and runs down the track.

   (a)

   Which energy store of the car increases as it is pulled to the top of the hill?

   [1 mark]

   • AKinetic
   • BElastic
   • CGravitational potential
   • DMagnetic

   (b)

   Ignoring friction, in which store is most of the car's energy at the bottom of the first hill?

   [1 mark]

   • AGravitational potential
   • BKinetic
   • CElastic
   • DNuclear

   (c)

   Describe the energy changes as the car runs down the hill, and explain why in practice it cannot climb a second hill as high as the first.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A pendulum clock in a museum in Prague has a brass bob of mass 0.50 kg that swings back and forth. Use a gravitational field strength of 10 N/kg.

   (a)

   The bob is lifted 0.40 m above its lowest point. What is its gravitational potential energy?

   [1 mark]

   • A0.20 J
   • B1.0 J
   • C20 J
   • D2.0 J

   (b)

   Ignoring friction, which statement about the bob at the lowest point of its swing is correct?

   [1 mark]

   • AIts kinetic energy is at a maximum and its gravitational potential energy is at a minimum
   • BIts kinetic energy is at a minimum and its gravitational potential energy is at a maximum
   • CIts kinetic energy and gravitational potential energy are both zero
   • DIts total energy is zero

   (c)

   The bob is released from a height of 0.40 m above its lowest point. Use conservation of energy to calculate its speed at the lowest point, ignoring air resistance.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   Students in Mexico City investigate how the release height of a 0.20 kg toy car on a ramp affects its speed at the bottom. A light gate measures the speed. The mean speeds were 1.3 m/s from a height of 0.10 m, 1.8 m/s from 0.20 m, 2.2 m/s from 0.30 m and 2.5 m/s from 0.40 m.

   (a)

   Outline two ways the students should make their data reliable and one safety precaution they should take.

   [3 marks]

   (b)

   Describe the pattern in the results and explain it using energy ideas. Suggest why the speeds are lower than they would be if no energy were wasted.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   An energy company in Switzerland plans a pumped-storage scheme. At night, when electricity is cheap, spare electricity pumps water from a lower lake up to a reservoir 300 m higher. When demand for electricity is high, the water runs back down through turbines to generate electricity. The reservoir holds 2.0 × 10⁶ kg of water. Use a gravitational field strength of 10 N/kg.

   (a)

   Discuss the benefits and drawbacks of building the pumped-storage scheme, and decide whether it should go ahead.

   [6 marks]

   (b)

   Calculate the gravitational potential energy lost when all the water falls 300 m. Assuming no energy is wasted, calculate the speed of the water at the bottom. Explain why the real speed would be lower, and state what the pumping process needs, at least, to refill the reservoir.

   [6 marks]

   Total for question 4: 12 marks

End of questions