5URg With à specific heat constant, c, of 2kJ/kg K. (a) Draw a sketch of the bullet and wooden block before impact and include an appropriate system boundary to allow the average temperature rise in the block to be found. (b) Write down the generalised version of the first law of thermodynamics for a system and identify the terms that are not relevant to the system identified in (a); hence find the average rise in temperature caused by the bullet lodging in the wooden block. [Answer: 0.011°C] 3. An insulated rigid container belonging to a kitchen blender is used to make a smoothie by liquidising some fruit, yogurt, honey and juice that together have a mass of 0.75kg and can be considered to have average specific heat capacity of 4.2 kJ/kg.K. (a) Draw a sketch of the blender and its contents and show the energy transfers across an appropriate system boundary for calculating the temperature rise in the smoothie ingredients when the blender is switched on. Use the first law of thermodynamics for a system to calculate the temperature rise in the smoothie ingredients after the blender blades have been powered for 5 minutes if the blender has a power rating of 500W and can be assumed to have an efficiency of 25%. (b) [Answer: 12°C] Y For instance, see: examples 2-3 to 2-15 and 4-2 to 4-10 in Çengell YA & Boles MA, Thermodynamics: An Engineering Approach, 6th Edition, New York: McGraw-Hill, 2008. UNIVERSITY OF LIVERPOOL