Scientific Investigation on Projectile Motion
Explore the concepts of hypothesis, variables, and controlled factors in scientific experiments through the investigations carried out by Sandile and Bongiwe. Sandile examines how adding sugar affects the volume of coffee, while Bongiwe investigates the impact of pellet distance on speed in a ballistic experiment.
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EXERCISE A Page 17 Skills
Skills 1. The theoretical answer or an educated guess as to what the answer will be to the scientific question. OR What the researcher thinks will happen. It should be formulated in the same way as the question. 2 Sandile notices that his cup of coffee becomes fuller when he adds sugar. He plans an investigation to determine how much fuller the cup becomes. Write the following for Sandile s investigation: Explain what a hypothesis is.
Skills 2.1 An investigative question that is verifiable. How will the volume of the coffee change when more sugar is added? 2.2 The independent variable The amount of sugar added. 2.3 The dependent variable The volume of the coffee
Skills 2.4 Controlled variable(s) The volume of the cup The temperature of the coffee 2.5 Constant(s) Specific heat capacity of water 3 Bongiwe carries out a ballistic experiment in an open field alongside an old mine dump for safety reasons. Bongiwe uses an air rifle. (Gauteng, June Exam Q1, 2012)
Skills Bongiwe investigates the impact that the distance travelled by the pellet has on the speed of the pellet. He fires an air rifle at a polystyrene ball, which is suspended from a light string. The pellet gets stuck in the polystyrene ball. He replaces the polystyrene ball after every shot. The polystyrene ball and the pellet swing away to the right, as shown in the diagram, to a height h. The mass of the pellet is 10 g and the mass of the polystyrene ball is 50 g. The experiment is repeated by increasing the range by 5 m each time, until the range is 20 m.
Skills 3.1 Formulate a suitable scientific (investigative) question for this experiment. How will the height that the ball reaches after it is hit by the pellet, be influenced by the distance the pellet travelled?
Skills 3.2 Formulate a hypothesis for the experiment. The height the ball reaches after being hit by the pellet, will decrease as the distance the pellet travels increases. 3.3 Identify the following variables: Independent variable The distance from which the pellet was fired. Dependent variable The height, h, to which the polystyrene ball will swing.
Skills Controlled variable(s) The air rifle The mass of the polystyrene ball Mass and type of pellets Wind conditions Gravitational acceleration Constant(s) Gravitational constant (G)
Skills 4 Use the following values showing the relationship between the independent quantity a and the dependent quantity m to answer the questions. 1 m 0,1 0,5 10 0,05 1,0 20 0,033 1,5 30 0,025 2,0 40 m a
Skills 4.1 Draw an accurate graph of m versus a. Provide a suitable heading for the graph and indicate all applicable values on the axes. The relationship between the quantities m and a
Skills 4.2 Identify the relationship between m and a. m is inversely proportional to a. 4.3 Give the relationship between m and a in mathematical terms. 1 m a
Skills 4.4 Use the third column of the table to make specific conversions of the values on the graph in order to obtain a new graph of1/mtagainst a, which is a straight line. Complete the table by writing the values and giving it a heading. m a 1 m 0,1 0,05 0,033 0,025 0,5 10 1,0 20 1,5 30 2,0 40
Skills 4.5 Draw an accurate straight line graph using the reworked data in the table. Provide a suitable heading for the graph and indicate all applicable values on the axes.
Skills The relationship between the inverse of m and a
Skills 4.6 Calculate the gradient of the graph in Question 4.5. y x 40 - 0 2,0 - 0 = 20 gradient = =
Skills 5 Say whether each of the following instances is an example of qualitative or quantitative research: 5.1 Traditional medicine Qualitative 5.2 The testing of Boyle s law Quantitative
Skills 5.3 Chemical titration Quantitative 5.4 Mopani worms used as a source of nutrition Qualitative
