Observations and Measurements

When a table tennis ball is dropped as shown in Fig. 4.1, it will bounce back upwards. Some of the initial gravitational potential energy (GPE) of the ball is lost in the bounce.

Plan an experiment to investigate how the height from which the ball is dropped affects the percentage of GPE lost in each bounce.

You may use any apparatus commonly found in a school laboratory in addition to the apparatus shown in Fig. 4.1.

GPE is given by the equation:

where $m$ is the mass of the ball, $g$ is the gravitational field strength and $h$ is the height above the bench from which the ball is dropped.

In your plan, you should:

• state what you will measure (dependent variable) and any additional apparatus you may use
• state any key variables to keep constant
• explain how you will ensure the results are as accurate as possible
• draw a table with column headings to display the results
• explain how you will use the results to draw a conclusion.

A student investigates the rate of cooling of hot water in a beaker.

Plan an experiment to investigate the relationship between the thickness of the cardboard insulation wrapped around the beaker and the rate of cooling of the hot water in the beaker.

The apparatus available includes:

• a supply of hot water
• a beaker
• a thermometer
• a supply of 1 mm thick cardboard sheets

In your plan include:

• any other apparatus needed
• a brief description of the method, including what you will measure and how you make sure that your measurements are accurate
• the variables you will control
• a results table to record your measurements (you are not required to enter any readings in the table)
• how you will process your results to reach a conclusion.

A student uses ice cubes to investigate the time taken for different masses of ice to melt when the ice cubes are placed in water.

Plan an experiment using ice cubes to investigate how the mass of ice affects the time taken for the ice to melt.

The following apparatus is available:

• top pan balance
• supply of ice cubes
• 250 $\text{cm}^3$ beaker
• supply of cold water
• stopwatch

You may also use other apparatus and materials that are usually available in a school laboratory.

In your plan, you should:

• explain briefly how to do the investigation
• state the key variables to keep constant
• draw a table, with column headings, to show how to display readings (you are not required to enter any readings in the table)
• explain how to use these readings to reach a conclusion.

You do not have to include a diagram of the apparatus you use but you may do so if it helps your plan.

Describe in detail how the student can obtain an accurate value for the outside diameter of the beaker.

In your account you should

• state the equipment used,
• explain how the equipment is used,
• state any readings taken,
• explain how the value for the diameter is obtained,
• describe how to make the measurement accurate.

The distance of each dot from A is $d$. Dot A was marked on the strip at time $t = 1.000\text{ s}$.

Take measurements from Fig. 1.1 and, in the space below, draw a table of results for $d$ against $t$.