39. a) An 18.0 kg curling stone is released with a speed of 4.0 m/s. What is its kinetic energy upon release? (3 marks) b) Determine the amount of thermal energy produced when an 18.0 kg curling stone that is released with a speed of 4.0 m/s slides to a stop over a distance of 30.0 m due to a 4.80 N force of kinetic friction. (3 marks) c) How do your answers to (a) and (b) compare? Explain. (2 marks) d) Given that the curling stone is moving and then comes to a stop, does this mean energy is lost? Explain. (2 marks) 46. a) If 79.2 kJ (79 200 )) of energy is transformed by a compact fluorescent light (CFL) bulb in 1.0 h (3600 s), what is the power rating of the bulb? (3 marks) b) When the total energy used by a CFL bulb is 300.0 kJ, 180.0 kj of energy is not wasted. Using these measurements, calculate the efficiency and percent efficiency of the CFL bulb. (4 marks) c) Evalute the effect on yourself and on the environment of switching a constantly used security light outside your home from an incandescent light bulb to a more efficient bulb. (2 marks) d) As you know, darker colours reflect less light than lighter colours. You can use this knowledge to propose a way to improve the sustainability of a dimmable can light or pot light (lighting that is recessed in a ceiling canister or pot). Assuming the canister light has a black interior and a CFL bulb (like the curly one in Figure 16.1), what could you do to the canister to improve the sustainability of this energy transformation technology? (2 marks) 47. When a 50.0 kg skier (initially at rest) skis down a ramp from a vertical height of 2.0 m, she attains a speed of 4.0 m/s. a) What is the skier's total mechanical energy at the top of the ramp? (3 marks) b) What is the skier's total mechanical energy at the bottom of the ramp? (3 marks) c) What is the percent efficiency of the ramp