Topic 1 - Energy (Practice Questions)

Question 1

The successful energy output from a car is kinetic energy.

The total energy output from the car is 1000kJ. The car transfers 500kJ to thermal energy and 300kJ to sound energy. Determine the kinetic energy generated [2]

Answer 1

• 500 + 300 = 800kJ
• 1000 - 800 = 200000J (200kJ)

Question 2

A skateboarder with a mass of 60 kg is practising on a half pipe.
She starts at the top, skates down one side and back up the other.

a). Describe the energy transfers involved [6]
b). The maximum speed the skateboarder reaches is 4 m/s. Calculate the kinetic energy at this point. [3]
c). The skater starts at a height of 2 m. Calculate the gravitational potential energy (g = 9.8 N/kg) [3]

Answer 2

a). • She starts with gravitational potential energy, • This shifts to kinetic as she skates down the slope, • When she is at the bottom, she has the max. amount of kinetic and min. amount of gravitational potential, • When she skates up to the other side, her store of kinetic energy concerts back to gravitational potential, • Through the whole process, some of the total energy is lost to the surroundings by sound, • and heat (thermal energy)

b). • Ek = 0.5mv^2, • 0.5 x 60 x 16, • 480J

c). Ep = mgh, • 60 x 9.8 x 2, • 1176J