Assignment 1a Solutions

Name: ______________________________Student no: _____________ Group:_______________ CC2404 Applied Physics and Instrumentation in Health Care Assignment 1A Duration: 30 min 1. When a rock falls freely, which of the following energy is constant? (Assuming no friction of air). A. Potential energy B. Mechanical energy C. Kinetic energy Answer:__B_ (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 producing cooling in order to control the body temperature. Increase in the flow rate of the blood to skin capillaries, sweating (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 3000 kcal one day and do nothing but sit for 18.0 h and sleep for the rest of the day? (assume that the energy consumption is 1.2 kcal/min for sleeping, and 1.8 kcal/min for sitting, 1 kcal = 4.186 kJ). Energy consumed=1.8 kcal/min x18x60min + 1.2 kcal/min x 6 x 60 min=2376kcal Energy stored=3000-2376=624 kcal=2612kJ Fat=2612/38.9=67.1 g (3 marks)

5. For every 50 J of electrical energy entering a television set, 7 J of useful light energy and 8 J of useful sound energy are produced. (a) Calculate the efficiency of the television set 7 J + 8J = 30% 50J

(1 marks)

(b) In which forms can the remaining energy be changed into? Give one example. Heat energy

(1 mark)

6. A woman has a mass of 55.0 kg in air and density of 1015.5 kg/m3 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). m

55 kg

3 her volume V = D = 1015 .5kg / m 3 = 0.05416 m , so buoyant force F = 0.05416 *1000 *10 = 541 N

(3 marks)