Lesson 2b - Formulating Hypothesis

There are 5 possible types of Science research, so 5 examples are given below:

Example 1: Test a Hypothesis

Different brands of handphones are tested for the radiation that they emit during standby, dial mode and receive mode.

(a) State the independent variable [1]

· different brands of handphones

(b) State the dependent variable [1]

·Radiation emitted from different handphones

(c) Suggest a hypothesis [1]

·      Samsung handphones have the greatest amount of radiation emitted 

(Note: There are no right or wrong answers, but just a reasonable guess)

(d) State 3 variables that you should keep constant. [3]

· Handphones should be fully charged.

· Handphones should be of the same battery capacity

· Handphones should be brand new

Example 2: Measure a value

The mass of Jupiter is calculated using the following steps:

·  Take pictures of Jupiter and its 4 moons every night over 30 days through a telescope at 8 pm. 

·  Plot a graph of the position of each of the 4 moons over 30 days.

·  Determine the period of each of the 4 moons.

·  Measure the distance between the moons and the center of Jupiter from the x-t graphs.

·  Plot a graph of T^2 against r^3.

·  Calculate the gradient.

·  Let gradient = 4pi^2/GM and calculate M since G is known.

·  Calculate the percentage error of the value of G. 

(a) State the independent variable. [1]

· the radius of different Jovian moons from the center of Jupiter 

(b) State the dependent variable. [1]

· the period of each of the Jovian moons 

(c) Suggest a hypothesis [1]

· The mass of Jupiter determined should be 1.898 × 10^27 kg and have a percentage error of less than 5%.

(Note: There are no right or wrong answers, just a reasonable guess)

(d) State 3 variables that you should keep constant. [3]

· All the photographs should be taken with the same magnification.

· All the photographs should be taken at the same time.

· All the photographs should be taken with the same sky conditions (e.g. clear skies) 

Example 3: Finding relationships

The rebound ratio is the ratio of the rebound height, divided by the dropped height. Use the rebound rating to measure the bounciness of new tennis balls vs. balls that have been used for 10, 20, 50, and 100 games.

(a) State the independent variable. [1]

· the number of times the tennis balls have been used (e.g. 0, 10, 20, 50, 100 games)

(b) State the dependent variable. [1]

·The rebound ratio = height of rebound / height where the tennis ball is dropped

(c) Suggest a hypothesis. [1]

·The more times the tennis ball is used, the lower is the rebound ratio

OR

·The more times the tennis ball is used, the higher is the rebound ratio

(Note: There are no right or wrong answers, just a reasonable guess)

(d) State 3 variables that you should keep constant. [3]

· Height at which the tennis ball is dropped.

· The tennis ball must be dropped vertically downwards.

· There should not be any draft (wind) that may cause the falling tennis ball to drift.

Example 4: Mathematical Modelling

It is observed that when a ball bearing falls down a column of water, the speed increases but up to a point. In order to create a Mathematical Model of the phenomenon, the following steps were taken:

· A high-speed video is taken of the ball bearing falling down the cylinder

· Using the video motion analysis software, a graph of velocity against time is created

· As it looks like a graph of V = A - Be^(-Ct + D), it was used to fit the data

· The coefficient of fit will tell us how close is the graph to the data 

(a) State the independent variable. [1]

· Time from the point at which the ball bearing is released

(b) State the dependent variable. [1]

· The velocity of the ball bearing.

(c) Suggest a hypothesis. [1]

· The velocity of the ball bearing varies with time in the following relation of V = A - Be^(-Ct + D)

(Note: There are no right or wrong answers, but just a reasonable guess)

(d) State 3 variables that you should keep constant. [3]

· Height at which the ball bearing is dropped

· The ball bearing must be dropped vertically downwards.

· The temperature of the experiment must be the same.

Example 5: Observational and Observatory Research 

A curious student wants to find out the soil quality around the school compound.

(a) State the independent variable. [1]

·Different locations around the school

(b) State the dependent variable. [1]

· The concentration of chemicals in soil such as Nitrates, Phosphorous, or Potassium.  

(c) Suggest a hypothesis. [1]

· The soil quality around the school is about the same.

(Note: There are no right or wrong answers, but just a reasonable guess) 

(d) State 3 variables that you should keep constant. [3]

· Depth at which the soil sample is collected

· Amount of soil collected at each site.

· Weather must be the same during the collection of the sample.