Assignment 1b Solutions

Name: ______________________________Student no: _____________ Group:_______________ CC2404 Applied Physics and Instrumentation in Health Care Assignment 1B Duration: 30 min 1.

What energy is described as being the energy due to its speed? a. nuclear energy, b. potential energy, c. kinetic energy Answer: __C _ (1 mark)

2. State three advantages and one disadvantage of infrared thermometer used for body temperature measurement. Advantages: 1. simple to use 2. less infection 3. fast response Disadvantage: 1. inaccuracy

(2 marks)

3. State two ways used by our bodies for keeping us warm in cold weather. Reduce in the flow rate of the blood to skin capillaries, reduce sweating, shivering. (‘goose skin’ not accepted) (2 marks)

4. Energy not used by human body for work is converted to fat. Each gram of fat can store 38.9 kJ of energy. How many grams of fat will you gain, if you eat 2500 kcal one day and do nothing but sit for 16.0 h and sleep for the rest of the day? (assume that the energy consumption is1.2 kcal/min for sleeping, and 1.8 kcal/min for sitting, 1 kcal = 4.186 kJ). Energy consumed=1.8 kcal/min x16x60min + 1.2 kcal/min x 8 x 60 min=2304kcal Energy stored=2500-2304=196 kcal=820kJ Fat=820/38.9=21.1 g (3 marks)

5. For every 100 J of electrical energy entering a television set, 10 J of useful light energy and 5 J of useful sound energy are produced. (a) Calculate the efficiency of the television set (10 J + 5J)/ 100 J = 15% (1 marks) (b) In which forms can the remaining energy be changed into? Give one example. Heat energy 6.

(1 mark)

A woman has a mass of 62.0 kg in air and density of 1013.9 kg/m 3 with the lungs empty. Find the buoyant force (in N) exerts on her, when she is completely in the water (given the density of water is 1000 kg/m3, 1 kg=10 N). her volume V = m/D = 62 kg /1013.9 kgm-3 = 0.06115 m3 so buoyant force F = 0.06115 * 1000 * 10 = 611.5 N

(3 marks)